Promotion of altered hepatic foci by 2,3,7,8-tetrachlorodibenzo-p-dioxin and 17beta-estradiol in male Sprague-Dawley rats.

The determination of differences in hormonal regulation of tumor promotion-related response to 2,3,7,8-tetrachlorodibenzop-dioxin (TCDD) between males and females may identify factors contributing to the female-specific hepatocarcinogenicity of TCDD in rats. In the current study, diethylnitrosamine-initiated male Sprague-Dawley rats were exposed to TCDD or corn oil vehicle in the presence and absence of 17beta-estradiol (E2), and cell proliferation and development of preneoplastic altered hepatic foci (AHF) were determined. After 30 weeks of exposure, gamma-glutamyltranspeptidase (GGT)-positive AHF and the number of placental glutathione-s-transferase (PGST)-positive AHF were significantly higher in TCDD-treated rats than in control rats. Both the number and volume fraction of GGT-positive AHF were significantly lower in rats cotreated with E2 regardless of TCDD exposure compared with corresponding non-E2-treated groups and were unaffected by TCDD. In contrast, the number of PGST-positive AHF was significantly higher in E2-treated rats in the absence of TCDD treatment. In addition, whereas E2 had no effect on the volume fraction of PGST-positive foci, the levels in rats cotreated with both E2 and TCDD were significantly higher than in controls. No differences were observed in cell proliferation between TCDD-treated and control rats, although cell proliferation was lower in rats exposed to E2 compared with placebo controls. The weaker potency of tumor promotion and lack of induction of cell replication and DNA damage in male rats likely explain the female-specific hepatocarcinogenicity of TCDD in chronic bioassays.     

Induction of altered hepatic foci by a mixture of dioxin-like compounds with and without 2,2',4,4',5,5'-hexachlorobiphenyl in female Sprague-Dawley rats

The hepatic tumor-promoting activity of a mixture of polyhalogenated aromatic hydrocarbons (PHAHs) was studied in a medium term two-stage initiation/promotion bioassay in female Sprague-Dawley rats. The PHAH mixture contained 2,3,7,8-tetrachlorodibenzo-p-dioxin (TCDD), 1, 2,3,7,8-pentachlorodibenzo-p-dioxin (PeCDD), 2,3,4,7, 8-pentachlorodibenzofuran (PeCDF), 3,3',4,4',5-pentachlorobiphenyl (PCB 126), 2,3',4,4',5-pentachlorobiphenyl (PCB 118), 2,3,3',4,4', 5-hexachlorobiphenyl (PCB 156), 2,2',4,4',5,5'-hexachlorobiphenyl (PCB 153) and covered >90% of the total toxic equivalents (TEQ) present in Baltic herring. To determine possible interactive effects of di-ortho-substituted PCBs, the PHAH mixture was tested with (PHAH+) and without (PHAH-) PCB 153. Rats were initiated by a diethylnitrosamine injection (30 mg/kg body wt i.p.) 24 h after a partial 23 hepatectomy. Six weeks after initiation, the PHAH mixtures were administered once a week by subcutaneous injections for 20 weeks. Treatment with the PHAH mixtures caused liver enlargement and an increased activity of the hepatic cytochrome P4501A1/2 and P4502B1/2. All PHAH exposure groups exhibited an increased occurrence of hepatic foci positive for the placental form of glutathione-S-transferase. In the PHAH-group dosed 1 microgram TEQ/kg body wt/week, the volume fraction of the liver occupied by foci was significantly lower compared to the TEQ equivalent dosed TCDD group (3.8 vs 8.7%). The volume fraction was significantly increased in the groups treated with 0.5, 1, or 2 micrograms TEQ/kg body wt/week of the PHAH+ mixture (4.5, 5.2, and 6.6%, respectively) compared to the corn oil group (2.0%), but to a lower extent than expected on basis of the TEQ doses. Overall, the TEQ-based administered dose overestimated the observed tumor-promoting effects of this PHAH mixture. The applicability of the toxic equivalency factor concept, the role of differences in toxicokinetic properties and interactive effects of PCB 153 on hepatic deposition of the dioxin-like congeners are discussed.     

The pharmacokinetics of [3H]1-[1-(2-thienyl)cyclohexyl]piperidine (TCP) in Sprague-Dawley rats

Using adult male Sprague-Dawley rats, we examined the blood protein binding and pharmacokinetics of the potent phencyclidine (PCP) receptor ligand 1-[1-(2-thienyl)cyclohexyl]piperidine (TCP). The average percentage of unbound [3H]TCP in rat serum was 42 +/- 6% and the [3H]TCP blood to plasma ratio was 0.98 +/- 0.03 (mean +/- SD, n = 5 in both studies). For the pharmacokinetic studies, [3H]TCP and 1 mg/kg unlabeled TCP were administered as an iv bolus dose. The average [3H]TCP elimination half-life was 2.1 hr. In contrast, total radioactivity in the plasma had a much longer half-life, suggesting much slower metabolite elimination. The average distribution volumes were 27 +/- 17, 15.6 +/- 6.2, and 5.6 +/- 3.0 liters/kg for V beta, Vss, and Vc, respectively. Total body and renal clearance values were 132 +/- 45 and 1.1 +/- 0.4 ml/min/kg, respectively. When TCP pharmacokinetic parameters were compared to PCP pharmacokinetic data in rats from a previous study, a strikingly similar pharmacokinetic profile was found. These data indicated that TCP and PCP are equivalent, from a pharmacokinetic point of view, and that the higher pharmacological potency of TCP over PCP is probably due to receptor-mediated differences.     

Multigenerational reproductive study of genistein (Cas No. 446-72-0) in Sprague-Dawley rats (feed study)

Genistein is a naturally occurring isoflavone that interacts with estrogen receptors and multiple other molecular targets. Human exposure to genistein is predominantly through consumption of soy products, including soy-based infant formula and dietary supplements. Consumption of soy and genistein has been associated with a variety of beneficial effects in animals and humans, but concerns have also been raised concerning potential adverse effects of genistein, particularly with regard to reproductive toxicity and the induction or potentiation of carcinogenesis, due primarily to its weak estrogenic activity. Because of these concerns, genistein was selected as one of the compounds to be examined in a protocol utilizing Sprague-Dawley rats to evaluate the effects of multigenerational and long-term exposures to doses of estrogenic agents that produce subtle reproductive tract lesions in developmentally exposed Sprague-Dawley rat pups. Results from the multigenerational reproductive toxicology feed study are reported in this report, and results of the 2-year feed study are reported separately (NTP, 2008a). Data from a preliminary reproductive dose range-finding feed study (NTP, 2007) that utilized exposure concentrations of up to 1,250 ppm genistein were used to select dietary exposure concentrations of 0, 5, 100, and 500 ppm for the current study. These dietary doses resulted in ingested genistein doses of approximately 0, 0.3, 7, or 35 mg genistein/kg body weight per day for males and 0, 0.5, 10, or 51 mg/kg per day for females during the time that the rats were directly consuming dosed feed. The current study was a multigenerational study (F(0) through F(4), with F(5) litters terminated at weaning) focused on reproductive endpoints. Animals were continuously exposed to genistein from the time that the F(0) generation was 6 weeks old through weaning of the F(3) generation, and animals of the F(0) through F(4) generations were sacrificed and necropsied on postnatal day 140 (PND 140). Dosed feed was removed from the F(3) pups at the time of weaning, and this generation and subsequent generations were maintained on control feed for the remainder of the study. For this study, 140 animals of each sex were obtained from the NCTR CD (Sprague-Dawley) rat colony at weaning and placed on a soy- and alfalfa-free diet that was used throughout the study in an attempt to maintain consistently low background exposure to phytoestrogens. Thirty-five animals per sex were assigned to exposure groups by a weight-ranked randomization procedure prior to the start of dietary exposure of the parental (F(0)) generation at 6 weeks of age. At the time of mating, males were paired with females from the same exposure group, and they were housed together until evidence of successful mating was detected or for a maximum of 14 days. Litters were randomly standardized to four males and four females on PND 2, and 25 litters per exposure group and their associated sires and dams were randomly selected to continue on study to produce the next generation and then necropsied at termination at 20 weeks of age (PND 140). Similar procedures were used to produce each generation. Results of the current study are summarized below. In the postweaning period, exposure to 500 ppm genistein reduced body weights predominantly in females of generations in which rats were ingesting the compound throughout adulthood (F(0) through F(2)). In the unexposed F(4) generation, female body weight was also depressed, although to a lesser extent than in the earlier generations. In the F(1) generation, postweaning body weights were reduced in all 100 and 500 ppm groups, with a more pronounced effect in the females. While pup birth weights were not significantly affected by genistein in the F(1) through F(4) generations (with the exception of 100 ppm males in the F(1) generation), both sexes showed depressed body weight gains during the preweaning period in the 500 ppm groups in all of these generations. Male pup preweaning body weight gains were also depressed in the 5 and 100 ppm groups in the F(1) generation. In the unexposed F(5) generation, pup birth weights in all exposed groups of both sexes were significantly lower than those in the controls, although it seems likely that this is a chance observation rather than a carryover effect from exposures in earlier generations. Measures of fertility were not adversely affected by genistein except for litter size. Litter size of the 500 ppm group in the F(2) generation was significantly smaller than that in the corresponding control group. The litter sizes in the F(1), F(2), and F(3) generations showed negative exposure concentration trends. Male and female 500 ppm pups in the F(1) generation had slightly reduced anogenital distances (AGDs) relative to controls when covaried by body weight. Female pups also had reduced AGDs in the F(2) (500 ppm) and F(3) (100 ppm) generations, although the statistical significance was dependent on the analysis method applied. Females exposed to 500 ppm showed an accelerated time of vaginal opening (approximately 3 days) in the F(1) and F(2) generations, while the 5 ppm group showed an earlier time of vaginal opening (1.3 days) in the F(3) generation. Body weight at vaginal opening was lower in 500 ppm females of the F(1) through F(3) generations and in the 5 ppm females of the F(1) generation. When examined shortly after vaginal opening, estrous cycles of 500 ppm females in the F(1) and F(2) generations were significantly longer (approximately 3 days and 1 day, respectively) than those of their respective control groups. Other estrous cycle disturbances (with the exception of decreased time in diestrus for 100 ppm females in the F(4) generation) were confined to the 500 ppm group of the F(1) generation and included reduced time in proestrus and an increase in the number and percentage of aberrant cycles. When the estrous cycles of older animals were examined prior to termination, the sole significant effects were a decreased time in estrus and increased time in diestrus in 5 ppm females of the F(2) generation and an increased number of abnormal cycles in 500 ppm females of the F(3) generation. No effects of genistein on male sexual development were noted with the exception of an increased time to testicular descent in 500 ppm males of the F(3) generation. Significant organ weight effects in both sexes were largely confined to single exposed groups in single generations; no clear patterns indicating toxicity to reproductive or nonreproductive organs were observed. Exposure-related microscopic lesions were confined to males, with the mammary gland and kidney affected. Incidences of mammary gland alveolar/ductal hyperplasia were significantly increased in 500 ppm males in the F(0) through F(2) generations and in 100 ppm males in the F(1) and F(2) generations. In the F(3) generation, a significant positive linear exposure concentration trend in the incidences of mammary gland hyperplasia occurred, but no exposed group differed significantly from the controls in pairwise comparisons. The more pronounced effect of genistein on the incidences of male mammary gland hyperplasia in the continuously exposed F(1) and F(2) generations as compared to the late adolescent and adult exposures of the F(0) generation and the preweaning-only exposure of the F(3) generation indicates that both developmental and adult exposures contribute to the maintenance of this effect into adulthood. Statistically significant effects of genistein on the incidences of generally minimal to mild kidney lesions in males were confined to the continuously exposed F(1) and F(2) generations. Incidences of renal tubule mineralization were significantly increased in 100 and 500 ppm males in the F(1) and F(2) generations, and incidences of inflammation and renal tubule regeneration were significantly increased in 500 ppm males in the F(1) generation. In addition to the results reported above for animals from the main study, ancillary studies were conducted with pups derived from the current study or from animals treated under similar conditions. These results have been reported elsewhere (Appendix P) and are not presented in detail in this report. Of particular importance are the data on blood and tissue genistein concentrations obtained from adult animals in the F(1) generation (Chang et al., 2000), from dams and fetuses (Doerge et al., 2001), and from dams and nursing pups (Doerge et al., 2006). These data provide measures of the internal dose resulting from the dietary exposure concentrations used in the current study and indicate that while fetal and adult exposures to genistein were at concentrations relevant to the full range of human exposures, only very low exposures were achieved during the early neonatal period when the pups were receiving exposures exclusively from the milk. The minimal exposure to genistein during this critical developmental period must be considered in the interpretation of the data derived from the current study. In summary, although genistein did show adverse effects with dietary exposures of 100 or 500 ppm, there were no clear adverse effects on the reproductive or developmental parameters measured at genistein concentrations ranging from less than 1 ppm (control diet) to 100 ppm, a range of doses producing serum concentrations achievable from the phytoestrogen content of human diets. There were few clear, overtly toxic effects that carried over across directly exposed generations or appeared to be imprinted to carry over into unexposed descendents under the conditions of exposure in this study. (ABSTRACT TRUNCATED).     

Reductive metabolism of the carcinogen 4-(5-nitro-2-furyl)thiazole to 1-(4-thiazolyl)-3-cyano-1-propanone by rat liver subcellular fractions

The reductive metabolism of 4-(5-nitro-2-furyl)thiazole (NFT), a rat mammary gland and forestomach carcinogen, was examined in vitro using rat liver tissues. NFT was reduced by rat liver cytosol or microsomes on anaerobic incubation with NADPH. The stoichiometry of microsomal reduction revealed that about 3 moles of NADPH were used per mole of NFT. Gas chromatographic analysis of the reaction mixture showed a major peak with a retention time of about 4.0 min in contrast to NFT with a retention time of about 6.5 min. Catalytic hydrogenation of NFT with palladium and activated carbon yielded a product with a retention time of 4.0 min. The component corresponding with the above metabolite was isolated from chemically reduced NFT and identified as 1-(4-thiazolyl)-3-cyano-l-propanone. The metabolite derived from enzymatic reduction had chromatographic and spectral properties and a mass spectral fragmentation pattern similar to those obtained chemically. These data establish that the enzymatically derived product is identical to that obtained by chemical reduction and that it corresponds to 1(4thiazolyl)3cyano1propanone.     

Toxicology and carcinogenesis studies of genistein (Cas No. 446-72-0) in Sprague-Dawley rats (feed study)

Genistein is a naturally occurring isoflavone that interacts with estrogen receptors and multiple other molecular targets. Human exposure to genistein is predominantly through consumption of soy products, including soy-based infant formula and dietary supplements. Consumption of soy and genistein has been associated with a variety of beneficial effects in animals and humans, but concerns have also been raised regarding potential adverse effects of genistein, particularly with regard to reproductive toxicity and the induction or potentiation of carcinogenesis, due primarily to its weak estrogenic activity. Because of these concerns, genistein was selected as one of the compounds to be examined using a protocol designed to evaluate the effects of multigenerational and long-term exposures to doses of estrogenic agents that produce subtle reproductive tract lesions in developmentally exposed Sprague-Dawley rat pups. Results from the 2-year study are reported here, and results from the multigenerational reproductive toxicology feed study are reported separately (NTP, 2008a). Data from a preliminary dose range-finding feed study (NTP, 2007) that utilized exposure concentrations up to 1,250 ppm genistein were used to select dietary exposure concentrations of 0, 5, 100, and 500 ppm for the current study. The multigenerational reproductive toxicology study examined F(0) through F(4) generations with F(5) litters terminated at weaning and focused on reproductive endpoints (NTP, 2008a). Animals were exposed from the time that the F(0) generation was 6 weeks old through weaning of the F(3) generation, and animals of the F(0) through F(4) generations were necropsied at 20 weeks of age. The current study was a 2-year dietary study utilizing three exposure arms: continuous exposure from conception through 2 years (designated F(1) continuous, or F(1)C), exposure from conception through 20 weeks followed by control diet to 2 years [designated F(1) truncated at postnatal day (PND) 140, or F(1)T140], and exposure from conception through weaning followed by control diet to 2 years (designated F(3) truncated at PND 21, or F(3)T21). The "F(3)" designation for the F(3)T21 arm indicates that these animals were siblings of the F(3) animals from the multigenerational reproductive toxicology study (NTP, 2008a). The F(1)C and F(1)T140 animals were also siblings but were derived from a separate breeding that was identical to the procedure used to produce the F(1) generation of the multigenerational reproductive toxicology study. The animals in this study were exposed to genistein during various phases of their lives from conception until termination at 2 years, and the ingested doses varied over the course of the study. During pregnancy, the ingested doses of the dams were approximately 0, 0.5, 9, or 45 mg/kg body weight per day. During lactation, the dams' ingested doses were 0, 0.7, 15, or 75 mg/kg per day. Supplementary studies, which are described in the multigenerational reproductive toxicology study, indicated minimal transfer of genistein to pups via the dams' milk. The mean directly ingested genistein doses during the period prior to PND 140 were approximately 0.4, 8, or 44 mg/kg per day for females and 0.4, 7, or 37 mg/kg per day for males. For the period between PND 140 and the end of the study, mean ingested doses were approximately 0.3, 5, or 29 mg/kg per day for females and 0.2, 4, or 20 mg/kg per day for males. For the current study, 50 animals per sex were initially assigned to each exposure group in each arm of the study. In control groups, histopathology data from one to four additional animals that had been assigned as sentinels but that became moribund or died early were also included in the analysis and presentation. Survival was similar in all control and exposed groups and ranged from 62% to 86% for males and 43% to 64% for females. Mean body weights of 500 ppm F(1)C females were less than those of the controls throughout the study. Mean body weights of 500 ppm F(1)T140 rats were less than those of the controls throughout the study. In females of all study arms (F(1)C, F(1)T140, and F(3)T21) an early onset of aberrant estrous cycles, suggesting early reproductive senescence, was observed in the 500 ppm groups. In the F(3)T21 arm, there were also significant effects on the onset of aberrant estrous cycles in the 5 and 100 ppm groups. Pituitary gland weights were significantly increased in females in the 500 ppm groups of the F(1)C and F(1)T140 study arms and in the 100 ppm group of the F(3)T21 arm. In F(1)C females, there was a significant positive trend in the incidences of mammary gland adenoma or adenocarcinoma (combined) regardless of whether an unmodified or natural log-transformed dose scale was used in the analysis, and the incidence in the 500 ppm group was significantly greater than that in the control group. A significant negative trend occurred in the incidences of benign mammary gland fibroadenoma in F(1)C females, and the incidence in the 500 ppm group was significantly less than that in the control group. In 5 and 100 ppm F(1)T140 females, the combined incidences of adenoma and adenocarcinoma were less than those in the control or 500 ppm groups, although these were not statistically significant differences. When the natural log-transformed dose scale was used, a marginally significant positive trend occurred in the incidences of adenoma or adenocarcinoma (combined) in F(3)T21 females. There were positive trends in the incidences of adenoma or carcinoma (combined) in the pars distalis of the pituitary gland of females in the F(1)C and F(1)T140 arms, and the incidence in the 500 ppm group was significantly greater than that in the controls in the F(1)C study arm. In F(1)C males, a significant positive trend (unmodified dose scale only) occurred in the incidences of combined adenoma or carcinoma of the pancreatic islets. While the incidence in the 500 ppm group was elevated relative to that in the control group (6/49 versus 1/49), this was not statistically significant. The fact that transitional lesions (i.e., hyperplasia) were not observed combined with variable control rates in males of this substrain of rats led to the conclusion that this lesion was not likely to be related to genistein treatment. CONCLUSIONS: Under the conditions of this 2-year feed study with continuous exposure to the test compound from conception through termination (F(1)C), there was no evidence of carcinogenic activity of genistein in male Sprague-Dawley rats exposed to 5, 100, or 500 ppm. There was some evidence of carcinogenic activity of genistein in female Sprague-Dawley rats based on increased incidences of mammary gland adenoma or adenocarcinoma (combined) and pituitary gland neoplasms. The incidence of benign mammary gland fibroadenoma in female rats was significantly decreased in the 500 ppm group. Under the conditions of this 2-year feed study with exposure to the test compound from conception through 20 weeks followed by control feed until termination (F(1)T140), there was no evidence of carcinogenic activity of genistein in male Sprague-Dawley rats exposed to 5, 100, or 500 ppm. There was equivocal evidence of carcinogenic activity of genistein in female Sprague-Dawley rats based on marginally increased incidences of pituitary gland neoplasms. Under the conditions of this 2-year feed study where offspring of three prior generations of animals exposed to the test compound were exposed from conception through weaning (PND 21) followed by control feed until termination (F(3)T21), there was no evidence of carcinogenic activity of genistein in male Sprague-Dawley rats exposed to 5, 100, or 500 ppm. There was equivocal evidence of carcinogenic activity of genistein in female Sprague-Dawley rats based on increased incidences of mammary gland adenoma or adenocarcinoma (combined). Exposure to genistein was also shown to accelerate the onset of aberrant estrous cycles in female Sprague-Dawley rats whether exposures were continuous or truncated at PND 140 or at weaning. The effects of genistein on estrous cycling and the incidences of common hormonally related spontaneous neoplasms of female Sprague-Dawley rats are consistent with an estrogenic mechanism of toxicity.     

The in vitro hepatic microsomal metabolism of 3,5-dimethyl-4-(phenylazo)-(1H)-pyrazole in rats

The in vitro hepatic microsomal metabolism of 3,5-dimethyl-4-(phenylazo)-(1H)-pyrazole (DMPAP) was studied using washed rat hepatic microsomal preparations fortified with NADPH. The substrate, DMPAP, and its potential metabolites, i.e. the corresponding reduction product, 3,5-dimethyl-4-amino-(1H)-pyrazole (DMAP), and the oxidation product, 3,5-dimethyl-4-(phenylazoxy)-(1H)-pyrazole (DMAPO), were synthesized and their structures elucidated by use of their spectral characteristics. DMPAP and its potential metabolites were then separated using a reverse phase HPLC system consisting of a C18 column and a mobile phase of acetonitrile:water (50:50) at a flow rate of 1 ml/min with UV detection at 254 nm. DMPAP was incubated with rat microsomal preparations, extracted into DCM in the presence of NaCl, and finally evaporated under a stream of nitrogen. The results from HPLC studies showed that DMPAP was metabolised to the corresponding reduction and oxidation products in the presence of NADPH.     

Pharmacokinetic, distribution, metabolism, and excretion of (Z)-2-amino-1,5-dihydro-1-methyl-5-[4-(mesyl)benzylidene]-4H-imidazol-4-one mesilate (ZLJ-601) in Sprague-Dawley rats

(Z)-2-amino-1,5-dihydro-1-methyl-5-[4-(mesyl)benzylidene]-4H-imidazol-4-one mesilate (ZLJ-601) is an imidazolone COX/5-LOX inhibitor, which has excellent anti-in?ammatory activity with an improved gastrointestinal safety profile. The purpose of this study was to evaluate the in vivo absorption, distribution, metabolism, and excretion of ZLJ-601 in Sprague-Dawley rats. After intravenous or intragastric administration to rats, the concentration of ZLJ-601 in plasma, bile, urine, feces and various types of tissues was detected by LC-MS. We also conducted the identification of metabolites using tandem mass spectrometry. After the intravenous administration, the t(1/2) ranged from 38.71 to 42.62 min and the AUC increased in a dose-proportional manner. After oral dosing, the plasma level of ZLJ-601 peaked at 28.33 min, having a C(max) value of 0.26 mg/l, and the bioavailability was only 4.92%. The highest tissue concentration of ZLJ-601 was observed in lung and kidney, but it was not found in brain. The majority of unchanged ZLJ-601 was excreted in urine (～35.87%) within 36 h. Two main metabolites are the hydroxylation product and the glucuronide conjugate of the hydroxylation product.     

Induction of hepatic CYP2B1/2 by a teratogenic compound cis-1-[-4-(p-menthane-8-yloxy)phenyl]piperadine (YM9429) in rats

A teratogenic compound cis-1-[-4-(p-menthane-8-yloxy)phenyl]piperadine (YM9429) selectively induces skeletal malformations characterized by cleft palate in rat fetuses. In the present study, we investigated the effect of YM9429 on hepatic cytochrome P-450s and their activities in rats. Oral administrations of YM9429 at a dose of 250, 500 or 750 mg/kg daily for 3 days induced cytochrome P-450 contents in a dose-dependent manner. Concomitant induction of enzyme activities of benzphetamine N-demethylase, erythromycin N-demethylase and, to a lesser extent, aminopyrine N-demethylase was observed. Immunoblot analysis revealed that YM9429 up-regulated hepatic levels of CYP2B1/2 and CYP3A1/2 proteins. A single dose of YM9429 at 250 mg/kg induced CYP2B1/2 protein levels significantly. These results suggest that YM9429 is a strong inducer of cytochrome P-450 with characteristics resembling those of phenobarbital.     

Hepatotoxicity and nephrotoxicity produced by 4-hydroxy-2-nonenal (4-HNE) following 4-week oral administration to Sprague-Dawley rats

4-Hydroxy-2-nonenal (4-HNE) is a major end product of lipid peroxidation of membrane n-6 polyunsaturated fatty acids, which are found in food products. In order to examine the toxicity attributed to 4-HNE, a subacute toxicity study was conducted in Sprague-Dawley (SD) rats. For this study, 4 groups of 10 male and 10 female rats were administered by gavage either 0 (control), 0.5, 2.5, or 12.5 mg 4-HNE/kg body weight/d for 28 d, and then sacrificed for blood and tissue sampling. No significant changes in body weight or clinical signs were observed, but biochemical analysis showed significant alterations in hepatotoxicity biomarkers, such as levels of serum albumin and total bilirubin, and aspartate aminotransferase (AST) activity, and in nephrotoxicity biomarkers, such as levels of blood urea nitrogen (BUN) and creatinine and activity of alkaline phosphatase (ALP), and urinary creatinine and protein levels at 0.5 mg/kg/d. In addition, significant increases in kidney and brain weights and a significant decrease in small intestine weight were noted at 12.5 mg/kg/d. Histologic examinations of kidneys showed hyaline droplets or accumulation of hyaline bodies in renal tubules and degeneration of tubular epithelium cells. These results demonstrate that oral daily exposure to 4-HNE for 28 d produced hepatotoxicity and nephrotoxicity. The no-observed-adverse-effect level (NOAEL) for 4-HNE was calculated to be <0.5 mg 4-HNE/kg/d.     

Effects of octamethylcyclotetrasiloxane (D4) on the luteinizing hormone (LH) surge and levels of various reproductive hormones in female Sprague-Dawley rats

The objectives of this study were to assess the potential for D₄ to suppress the pre-ovulatory lutenizing hormone (LH) surge, to block or delay ovulation, and to evaluate potential effects on reproductive hormones in rats. Female Sprague–Dawley Crl:CD^® (SD) IGS BR rats received whole-body vapor inhalation exposure to D₄ (0, 700, or 900 ppm) 6 h per day for 3 days. Trunk blood obtained on proestrus at 10 a.m. was evaluated for levels of follicle stimulating hormone (FSH), estradiol (E2), estrone (E1), and progesterone (P4). Other rats had serial blood samples collected via cannula at 2, 4, 6, 8, and 10 p.m. on the day of proestrus and plasma evaluated for LH and prolactin (PRL). Trunk blood was collected at 8 a.m. of estrus and plasma evaluated for FSH, E2, E1, and P4. At 10 a.m. on proestrus, significant increases in E1 levels in the 700 and 900 ppm groups and significant increases in P4 levels in the 900 ppm group were noted. At 8 a.m. on estrus, significant increases in E1, E2, in the E1/E2 ratio and decreases in FSH were noted in the 700 and 900 ppm groups. The major effect on the LH profile was observed most clearly when the rats were grouped by ovulatory status, animals that did or did not ovulate. Regardless of treatment, suppression of the LH surge correlated with blocked ovulation. The percentage of rats that ovulated was (700 ppm, 42%; 900 ppm, 31%) compared to controls (79%). Overall, the data indicate that high exposures to D₄ attenuated the pre-ovulatory LH surge and significantly decreased the portion of female rats that ovulated.     

Pharmacological properties of 1-(4-methoxybutylamino)-2-(1-4-benzodioxan-2-yl)-ethane (2802 IS)

Summary The pharmacological properties of 1-(4-methoxybutylamino)-2-hydroxy-2-(1,4-benzodioxan-2-yl) ethane (2802 IS) are described. 2802 IS when administered by vein to anesthetized dogs and cats in doses of 0.025-0.05 mg/kg lowered the blood pressure. In an instrumental reward discrimination exercise in rabbits the depressant effects of the compound were demonstrated at 0.25-0.5 mg/kg i.v. 2802 IS provokes significant changes of the cortical and subcortical electrical activity of the unanaesthesized rabbit and a dampening of the arterial pressure response to the electrical stimulation of the hypothalamus. The site of action of the central effect of the compound is discussed.This work has been supported in part by a Grant from the National Institute of Mental Health, U.S.A. (MH-07093).     

N-Methyl-1-(4-methoxyphenyl)-2-aminopropane (PMMA) and N-Methyl-1-(3,4-methylenedioxyphenyl)-2-aminopropane (MDMA) produce non-identical discriminative stimuli in rats

N-Methyl-1-(3,4-methylenedioxyphenyl)-2-aminopropane (methylenedioxymethamphetamine, MDMA, Ecstasy) and its structurally abbreviated congener N-methyl-1-(4-methoxyphenyl)-2-aminopropane (para-methoxymethamphetamine, PMMA) are chemically related designer drugs, and PMMA is sometimes sold on the clandestine market as a substitute for MDMA. Prior drug discrimination studies have found that MDMA and PMMA substitute for one another suggesting that they produce similar discriminative stimulus effects in rats. However, there also are some indications that the two agents produce distinct stimulus effects. In this study, further comparisons were made between the stimulus effects of these two agents. Sprague-Dawley rats were trained to discriminate either 1.25 mg/kg of PMMA or 1.5 mg/kg of MDMA from saline vehicle in a two-lever operant paradigm. A structure-activity comparison revealed that MDMA and PMMA behave similarly upon homologation of their terminal amine substituents. In contrast, the PMMA stimulus, unlike an MDMA stimulus, failed to generalize completely to the psychostimulant cocaine, 8-hydroxy-2-(N,N-di-n-propylamino)tetralin (8-OH DPAT), and R(-)-1-(3-methoxyphenyl)-2-aminopropane [R(-)MMA]. In an additional group of animals, a (+)amphetamine stimulus partially generalized to R(-)MMA. Taken together, the results argue and re-emphasize the conclusion that the stimulus effects produced by MDMA and PMMA are similar, but non-identical, and that PMMA is the less "stimulant-like" of the two.     

Repeated dose toxicity and relative potency of 1,2,3,4,6,7-hexachloronaphthalene (PCN 66) 1,2,3,5,6,7-hexachloronaphthalene (PCN 67) compared to 2,3,7,8-tetrachlorodibenzo-p-dioxin (TCDD) for induction of CYP1A1, CYP1A2 and thymic atrophy in female Harlan Sprague-Dawley rats

In this study we assessed the relative toxicity and potency of the chlorinated naphthalenes 1,2,3,4,6,7-hexachloronaphthalene (PCN 66) and 1,2,3,5,6,7-hexachloronaphthalene (PCN 67) relative to that of 2,3,7,8-tetrachlorodibenzo-p-dioxin (TCDD). Chemicals were administered in corn oil:acetone (99:1) by gavage to female Harlan Sprague-Dawley rats at dosages of 0 (vehicle), 500, 1500, 5000, 50,000 and 500,000ng/kg (PCN 66 and PCN 67) and 1, 3, 10, 100, and 300ng/kg (TCDD) for 2 weeks. Histopathologic changes were observed in the thymus, liver and lung of TCDD treated animals and in the liver and thymus of PCN treated animals. Significant increases in CYP1A1 and CYP1A2 associated enzyme activity were observed in all animals exposed to TCDD, PCN 66 and PCN 67. Dose response modeling of CYP1A1, CYP1A2 and thymic atrophy gave ranges of estimated relative potencies, as compared to TCDD, of 0.0015-0.0072, for PCN 66 and 0.00029-0.00067 for PCN 67. Given that PCN 66 and PCN 67 exposure resulted in biochemical and histopathologic changes similar to that seen with TCDD, this suggests that they should be included in the WHO toxic equivalency factor (TEF) scheme, although the estimated relative potencies indicate that these hexachlorinated naphthalenes should not contribute greatly to the overall human body burden of dioxin-like activity.     

Progesterone withdrawal increases the alpha4 subunit of the GABA(A) receptor in male rats in association with anxiety and altered pharmacology - a comparison with female rats

Withdrawal from the neurosteroid 3alpha,5alpha-allopregnanolone after chronic administration of progesterone increases anxiety in female rats and up-regulates the alpha4 subunit of the GABA(A) receptor (GABA(A)-R) in the hippocampus. We investigated if these phenomena would also occur in male rats. Progesterone withdrawal (PWD) induced higher alpha4 subunit expression in the hippocampus of both male and female rats, in association with increased anxiety (assessed in the elevated plus maze) comparable to effects previously reported. Because alpha4-containing GABA(A)-R are insensitive to the benzodiazepine (BDZ) lorazepam (LZM), and are positively modulated by flumazenil (FLU, a BDZ antagonist), we therefore tested the effects of these compounds following PWD. Using whole-cell patch clamp techniques, LZM-potentiation of GABA ((EC20))-gated current was markedly reduced in CA1 pyramidal cells of male rats undergoing PWD compared to controls, whereas FLU had no effect on GABA-gated current in control animals but increased it in PWD animals. Behaviorally, both male and female rats were significantly less sensitive to the anxiolytic effects of LZM. In contrast, FLU demonstrated significant anxiolytic effects following PWD. These data suggest that neurosteroid regulation of the alpha4 GABA(A)-R subunit may be a relevant mechanism underlying anxiety disorders, and that this phenomenon is not sex-specific.     

含哌嗪环的三唑醇类化合物的合成及体外抗真菌活性

目的设计合成含哌嗪环侧链的三唑醇类化合物并研究其体外抗真菌活性。方法以2-氯-2′,4′-二氟苯乙酮为起始原料经多步反应合成目标化合物，化合物结构经IR、^1H-NMR谱确证；选择8种真菌为实验菌株，按国际标准抗真菌敏感性实验方法测定体外抑菌活性。结果设计合成了11个新化合物。所有目标化合物对8种真菌均具有一定的抑制作用。结论多个目标化合物的抗真菌活性明显高于阳性对照药氟康唑，其中化合物11具有广谱、高活性的优点，其体外抗真菌活性与对照药伊曲康唑相当，有进一步研究开发的价值。     

Disposition and metabolism of 2-(2'(1',3'-dioxolan-2-yl)-2- methyl-4-(2'-oxopyrrolidin-1-Yl)-6-nitro-2h-1-benzopyran (SKP-450) in rats.

The disposition and metabolism of the new antihypertensive agent 2-(2"(1", 3"-dioxolan-2-yl)-2-methyl-4-(2'-oxopyrrolidin-1-yl)-6-nitro -2H-1-benzopyran (SKP-450) were investigated in male rats after single oral and i.v. doses of 14C-labeled compound. After an oral 2.0 mg/kg dose, mean radiocarbon recovery was 98.2 +/- 2.3% with 31.1 +/- 7.3% in the feces and 67.1 +/- 14.3% in the urine. Biliary excretion of radioactivity for the first 24-h period was approximately 40%, suggesting that SKP-450 is cleared either by hepatobiliary excretion or by renal excretion. SKP-450 was well absorbed; bioavailability calculated on the basis of radioactivity was 68 to 97%. Tissue distribution of the radioactivity was widespread with high concentrations in the liver and kidney but low central nervous system penetration. Radio-HPLC analysis of bile and urine from rats indicated the extensive metabolism of SKP-450 into oxidative metabolites. Oxidative metabolism of the dioxolanyl ring resulted in an aldehyde intermediate, subsequently confirmed in vitro, which was further oxidized to the corresponding carboxylic acid (M1) or reduced to the corresponding alcohol (M3). No parent drug was detected in the urine or bile. Glucuronide conjugate of M3 was also detected in urine and bile, accounting for 5.8 +/- 2.1 and 8.9 +/- 3. 7% of the excreted radioactivity, respectively. Quantitative data obtained from plasma samples suggest that the majority of circulating radioactivity was associated with metabolites. Our results suggest that the long duration of pharmacological activity of SKP-450 (>10 h) is largely attributable to its metabolites.