Uterotrophic assay,Hershberger assay,and subacute oral toxicity study of 3-amino-1,2,4-triazole based on the Organization for Economic Co-operation and Development draft protocols

We performed a uterotrophic assay, the Hershberger assay, and the 28-day repeated-dose toxicity study (enhanced OECD test guideline no. 407) of 3-amino-1,2,4-triazole based on the OECD draft protocols. In the uterotrophic assay, female SD rats were subcutaneously injected with the chemical at doses of 0, 100, 300, and 1,000 mg/kg on each of 3 days from postnatal day 20 to day 22, and no changes were observed. In the Hershberger assay, the test chemical was orally administered at doses of 0, 40, 200, and 1,000 mg/kg/day to castrated male Wistar rats for 10 consecutive days beginning on postnatal day 56, and no androgen agonistic and antagonistic changes were observed. Alternatively, when the test chemical was orally administered at doses 0, 5, 25, and 125 mg/kg/day for at least 28 days in the subacute oral toxicity study, thyroid follicular epithelial cell hypertrophy with increased thyroid weights was detected in the male and female rats in 25 and/or 125 mg/kg groups, and hypertrophy of the anterior pituitary cells with increased pituitary weights in male and female rats was also observed in the 125 mg/kg group. Furthermore, serum T3 and T4 values decreased and serum TSH values increased in male and female rats in the 125 mg/kg group. Therefore, 3-amino-1,2,4-triazole was concluded to have anti-thyroid acting as endocrine-mediated effects, but no estrogenic or androgenic effects. In addition, decreased body weight, and abnormal biochemical parameters attributed to thyroid, liver or kidney dysfunction were observed in male and female rats in the 25 and/or 125 mg/kg groups.     

Uterotrophic assay, Hershberger assay, and subacute oral toxicity study of 4,4′-butylidenebis(2-tert-butyl-5-methylphenol) and 3-(dibutylamino)phenol, based on the OECD draft protocols

We performed a uterotrophic assay, the Hershberger assay, and a 28-day repeated-dose toxicity study [enhanced Organization for Economic Co-operation and Development (OECD) test guideline No. 407] of 4,4'-butylidenebis(2-tert-butyl-5-methylphenol) and 3-(dibutylamino)phenol, based on the OECD draft protocols. In the uterotrophic assay of 4,4'-butylidenebis(2-tert-butyl-5-methylphenol), female SD rats were subcutaneously injected with the chemical at doses of 0, 100, 300, and 1,000 mg/kg on each of 3 days from postnatal day 20 to day 22, and no changes were observed. In the Hershberger assay of 4,4'-butylidenebis(2-tert-butyl-5-methylphenol), the test chemical was orally administered to castrated male SD rats at doses of 0, 50, 200, and 1,000 mg/kg/day for ten consecutive days beginning on postnatal day 56, and no changes were observed. When this chemical was orally administered at doses 0, 5, 25, and 125 mg/kg/day for at least 28 days in the subacute oral toxicity study, an increase in thyroid weight was observed in the female rats in the 125 mg/kg group, an increase in serum thyroid-stimulating hormone (TSH) values in the male and female rats in the 125 mg/kg group, and a decrease in serum T3 and T4 values in the male rats in the 125 mg/kg group, and thyroid follicular epithelial cell hypertrophy was observed in some of the female rats in the 125 mg/kg group. These findings were concluded to be the result of endocrine-mediated effects of the chemical on thyroid function. In addition, increased liver weight, abnormal histological findings in the liver, and abnormal biochemical parameters related to liver function were observed in male and/or female rats in 5 mg/kg group and higher dose groups. The no-observed-effect level for 4,4'-butylidenebis(2-tert-butyl-5-methylphenol) was concluded to be <5 mg/kg/day. In the uterotrophic assay of 3-(dibutylamino)phenol, female SD rats were subcutaneously injected with the chemical at doses of 0, 100, 300, and 1,000 mg/kg on each of 3 days from postnatal day 20 to day 22, and no changes were observed. In the Hershberger assay of 3-(dibutylamino)phenol, the test chemical was orally administered at doses of 0, 50, 200, and 400 mg/kg/day to castrated male SD rats for ten consecutive days beginning on postnatal day 56, and no changes were observed. On the other hand, when this test chemical was orally administered at doses 0, 30, 100, and 300 mg/kg/day for at least 28 days in the subacute oral toxicity study, thyroid weight increased in the male rats in the 300 mg/kg group, thyroid follicular epithelial cell hypertrophy was observed in a small number of male rats in the 300 mg/kg group, serum T3-values decreased in the female rats in the 300 mg/kg group, and a tendency for TSH-values to increase was observed in the male and female rats in the 300 mg/kg group. Therefore, 3-(dibutylamino)phenol was also concluded to have slight anti-thyroid acting effects as the endocrine-mediated effects. On the other hand, increased hemosiderin deposition in the spleen, increased spleen weight, hematological abnormalities, and squamous epithelial hyperplasia of the forestomach were detected in male and/or female rats in the 100 and/or 300 mg/kg groups, and thus the no-observed-effect level for 3-(dibutylamino)phenol was concluded to be 30 mg/kg/day.     

Ameliorative effect Trichosanthes dioica root against experimentally induced arsenic toxicity in male albino rats

The present study evaluated the ameliorative potential of hydroalcoholic extract of Trichosanthes dioica root (TDA) against arsenic induced toxicity in male albino rats. TDA (5 and 10mg/kg) was administered orally to rats for 20 consecutive days before oral administration of sodium arsenite (10mg/kg) for 8 days. Then the body weights, organ weights, haematological profiles, serum biochemical profile; hepatic and renal antioxidative parameters viz. lipid peroxidation, reduced and oxidized glutathione, glutathione-S-transferase, glutathione peroxidase, glutathione reductase, superoxide dismutase, catalase and DNA fragmentation were evaluated. Pretreatment with TDA markedly and significantly normalized body weights, organ weights, haematological profiles, serum biochemical profile and significantly modulated all the hepatic and renal biochemical parameters and reduced DNA fragmentation in arsenic intoxicated rats. The present findings conclude that T. dioica root possessed remarkable ameliorative effect against arsenic induced organ toxicity in male albino rats mediated by alleviation of arsenic induced oxidative stress by multiple mechanisms.     

Prechronic Inhalation Toxicity Studies of 2-Mercaptobenzimidazole (2-MBI)in F344/N Rats

2-Mercaptobenzimidazole (2-MBI), used in rubber processing,is a suspect carcinogen structurally related to ethylene thiourea.The inhalation toxicity of 2-MBI was evaluated in male and femaleF344/N rats exposed 6 hr/day, 5 days/week to respirable aerosolsgenerated by spray atomization of aqueous suspensions of the2-MBI powder and subsequent drying of the resulting aerosols.Twelve exposures at target concentrations of 0, 6.3, 12.5, 25.0,50.0, or 100 mg/m³ of 2-MBI produced a dose-related reductionin body weight gains, thyroid follicular cell hyperplasia, adrenalcortex fatty change, and pituitary atrophy. Sub-chronic exposureswere conducted at target concentrations of 0, 3.1, 6.2, 12.5,25.0, and 50.0 mg/m³ of 2-MBI. Rats at 25 mg/m³ displayed hunchedposture, hypoactivity, and reduced body weight gain, with compoundrelated mortality at the highest exposure level. Anemia; increasedSGPT, SGOT, alkaline phosphatase, sorbitol dehydrogenase, BUN,and cholesterol; and reduced free fatty acid were seen in ratsat 25 mg/m³. Increased thyroid weight and thyroid follicularcell hyperplasia were noted in both sexes at 6.2 mg/m³, withreduced triiodothyronine and thyroxine levels in both sexesat > 12.5 mg/m³. Thyroid follicular cell hyperplasia wasalso seen in rats at 3.1 mg/m³. Thymus weights were significantlyreduced in both sexes at all exposure levels with liver weightincreases at 6.2 mg/m³. Exposure-related histopathologic changesincluded pituitary cytoplasmic vacuolization, adrenal cortexnecrosis, lymphoid depletion, thymic atrophy, liver cell hypertrophy,renal mineralization and tubular atrophy, and hypocellularityof the bone marrow.     

Comparative toxicokinetic/toxicodynamic study of rubber antioxidants, 2-mercaptobenzimidazole and its methyl substituted derivatives,by repeated oral administration in rats

2-Mercaptobenzimidazole (MBI), a rubber antioxidant, is known to exhibit potent thyroid toxicity in rats, whereas its methylated derivatives are much less toxic. To characterize this methyl-substituent effect on the thyroid toxicity of MBI, comparative toxicokinetic analyses have been conducted in the present study. MBI and the MMBIs [4-methylated MBI (4-MMBI) and 5-methylated MBI (5-MMBI), and a 1:1 mixture of these 4- and 5-methylated isomers (MMBI mix)] suspended in corn oil were repeatedly administered (at 0.3-0.6 mmol/kg) to male Wistar rats by gavage once daily for 2 weeks. After the first and last administrations, blood and urine samples were collected, and the levels of unchanged compounds and their desulfurated metabolites were determined by high performance liquid chromatography. After repeated oral administration (roa), the C(max) and area under concentration-time curve (AUC) of MBI were markedly increased, while the MMBIs essentially were cleared from the blood within 10 h. After roa, the C(max) and AUC of 4-MMBI decreased markedly, suggesting metabolic enzyme induction. However, the toxicokinetic parameters of 5-MMBI were not markedly altered by roa. The inhibitory potencies (IC(50)) against lactoperoxidase of MBI, 4-MMBI, and 5-MMBI were 20.6 micro M, 45.6 micro M and 31.6 micro M, respectively. Thus, we suggest that the marked decrease of thyroid toxicity by methyl substitution of MBI is caused mainly by a decrease in systemic exposure to the compounds and partly by a decrease in inhibition of thyroid hormone synthesis.     

Safety evaluation studies on oxisuran,a differential inhibitor of cell-mediated hypersensitivity

Preclinical toxicity studies were conducted on oxisuran, 2-[(methylsulfinyl) acetyl]-pyridine, an immunosuppressant with selective inhibition of cell-mediated hypersensitivity. Oral LD50 values were 5280 and 6610 mg/kg in female mice and rabbits, respectively, and 6550 mg/kg in female and male rats. An LD50 could not be established in dogs because of emesis at a dose of 5000 mg/kg. Intravenous LD50 values were 2510 mg/kg for mice and 1800 mg/kg for female and male rats. Feeding the drug in the diet to rats at dosages of 20, 100, 300, and 1000 mg/kg for 13 weeks caused a slight reduction in food consumption and body weight gain at the higher dosages. At doses of 100, 300, and 1000 mg/kg, cloudy swelling and fatty infiltration of the liver and hyperplasia of the thyroid occurred in dose-related patterns (mild to moderate) in many animals. No significant changes were found in thyroid function studies which included thyroid uptake (¹²⁵I) and T₃ and T₄ determinations. The thyroid hyperplasia seen at 13 weeks disappeared within a few days of drug withdrawal. Oral daily administration of 20, 125, 500, and 2000 mg/kg of oxisuran to dogs for 13 weeks produced a decrease in food consumption and body weight in the latter phase of the study in the males treated with the high dose. Serum glutamic-pyruvic transaminase was mildly elevated in dogs given 2000 mg/kg. At this dose, some animals showed slightly increased thyroid and liver weights. Histologically, thyroid hyperplasia was moderate in females (2000 mg/kg) and mild to moderate in males (125, 500, and 2000 mg/kg). The liver, in the animals of the high-dose group showed a slight degree of vacuolar changes and bile retention. Thyroidal radioiodine uptake (¹²⁵I), PBI, TI, and serum cholesterol were slightly below normal values. The histology and function tests of the thyroid were within normal ranges at 4 weeks post-treatment.     

Effect of chlorpyrifos-methyl on steroid and thyroid hormones in rat F0- and F1-generations

Chlorpyrifos-methyl (CPM) suppressed androgenic activity in Hershberger assay using castrated rats. Acute oral lowest-observed-adverse-effect-level (LOAEL) and no-observed-adverse-effect-level (NOAEL) was evaluated as 12 and 0.1 mg/kg bw, respectively, based on its major effect of cholinesterase inhibition. Also, repeated oral NOAEL was 0.1 mg/kg bw/day based on adrenal damage in rats. We investigated one-generation reproductive toxicity of CPM focusing on endocrine-disrupting effects by the administration of 1, 10 and 100 mg/kg bw/day CPM to mature SD rats (F0) through pre-mating, mating, gestation and lactation period and to their offspring (F1) until 13 weeks age via gavage. A group treated with corn oil served as vehicle control.

In F0 rats, the most affected organs were adrenal glands as increased in weight at all doses of CPM in males and at 10 and 100 mg/kg CPM in females and adrenal vacuolation at CPM 10 and 100 mg/kg. The relative and absolute ovaries and the absolute seminal vesicle weights were decreased but the weights of liver, spleen or kidneys were increased at 100 mg/kg CPM.

Parameters representing reproductive performances as mating ratio, gestation length and delivery index were not affected, except for decreased fertility index and numbers of implantation and born pups and a higher male sex ratio of pups at CPM 100 mg/kg.

F1 pups exposed to CPM 100 mg/kg in utero and via maternal milk showed lower body weight with changes of absolute or relative weights of brain, ovary, liver, spleen and epididymis and decreased absolute not relative anogenital distance at weanling time. The time of vaginal patency and preputial separation and estrous cycling pattern of F1 rats were not impacted by CPM. After further 10 weeks oral administration until 13 weeks old, adrenal glands, brain, liver, spleen or kidneys tended to be increased, while thyroid gland, testes and ventral prostate of F1 male rats were decreased at CPM 10 or 100 mg/kg. Histopathologically, necrosis or vacuolation of thyroid follicular epithelial cells and adrenal cortical cells were observed at all doses of CPM. Serum levels of estradiol, testosterone, T4 and T3 were significantly lower while TSH and cholesterol were higher in both F1 female and male rats treated with CPM though dose-responsiveness was not clear in F1 females. Decreased sperm were counted in F1 rats at CPM 100 mg/kg. As a whole, LOAEL and NOAEL was evaluated as 10 and 1 mg/kg bw, respectively, based on decreased estradiol and T4 and increased TSH in serum of F1 male rats, and when considering histopathological alteration of adrenal and thyroid glands, LOAEL assumed to be lower than 1 mg/kg bw.

This study elucidates that CPM exhibit weak reproductive toxicity in F0 rats exposed at adulthood and negligible effects in F1 offspring exposed in utero and via lactation at weanling, but induce anti-androgenic effect and hypothyroidism after long term exposure from in utero through sexual maturation of F1 rats.     

The Effects of Triclosan on Puberty and Thyroid Hormones in Male Wistar Rats

Triclosan (5-chloro-2-(2,4-dichlorophenoxy)phenol) is a potentantibacterial and antifungal compound that is widely used inpersonal care products, plastics, and fabrics. Recently triclosanhas been shown to alter endocrine function in a variety of species.The purpose of this study was to determine effects of triclosanon pubertal development and thyroid hormone concentrations inthe male rat. Weanling rats were exposed to 0, 3, 30, 100, 200,or 300 mg/kg of triclosan by oral gavage from postnatal day(PND) 23 to 53. Preputial separation (PPS) was examined beginningon PND 33. Rats were killed on PND 53, organ weights were recordedand serum was collected for subsequent analysis. Triclosan didnot affect growth or the onset of PPS. Serum testosterone wassignificantly decreased at 200 mg/kg, however no effects wereobserved on androgen-dependent reproductive tissue weights.Triclosan significantly decreased total serum thyroxine (T4)in a dose-dependent manner at 30 mg/kg and higher (no observedeffect level of 3 mg/kg). Triiodothyronine (T3) was significantlydecreased only at 200 mg/kg, but thyroid stimulating hormonewas not statistically different at any dose. Liver weights weresignificantly increased at 100 mg/kg triclosan and above suggestingthat the induction of hepatic enzymes may have contributed tothe altered T4 and T3 concentrations, but it does not appearto correlate with the T4 dose-response. This study demonstratesthat triclosan exposure does not alter androgen-dependent tissueweights or onset of PPS; however, triclosan exposure significantlyimpacts thyroid hormone concentrations in the male juvenilerat.     

The Adverse Effects of Oral 2-Mercaptobenzimidazole on Pregnant Rats and Their Fetuses

The effects of oral 2-mercaptobenzimidazole (2-MBI) on pregnantWistar rats were examined. In a preliminary dose-finding study,pregnant rats treated with 2-MBI over Days 7–17 of gestationshowed reduction in maternal thymus weights with compound-relatedmortality at doses40 mg/kg. No adverse effects on fetuses werefound at doses 40 mg/kg. However, anasarca, cleft palate, anddilated lateral ventricles were present in all fetuses fromthe only survivor among the dams treated with 60 mg/kg of 2-MBI.In the teratology study, pregnant rats were treated with 2-MBIat doses of 0, 3.3, 10, and 30 mg/kg during the period of organogenesis(Gestation Days 7–17). In addition, pregnant rats of threegroups were also treated with 60 mg/kg of 2-MBI for 3 or 4 daysduring specific periods of organogenesis (Days 7–10, 11–14,or 15–17 of gestation). Treatment on Gestation Days 7–17resulted in reduced maternal thymus weights at doses of 3.3mg/kg. In addition to reduced fetal weights, visceral variations(kinked ureter and dilated renal pelvis) and delayed ossificationwere seen in the fetuses at doses 10 mg/kg, and skeletal variations(rudimentary lumbar ribs) were seen at 30 mg/kg. In the fetusesfrom the dams treated with 60 mg/kg of 2-MBI, rudimentary lumbarribs were seen mainly in the group treated on Days 7/10 of gestation,whereas kinked ureter and dilated renal pelvis were evidentmainly in the group treated on Gestation Days 15/17. Dilatedlateral ventricles and cleft palate were present only in thegroup treated with 60 mg/kg on Days 11–14 of gestation,though 5 out of 16 dams died during the study. In conclusion,maternal toxicity preceded fetal toxicity and major fetal malformationswere seen only at a dose (60 mg/kg) which was lethal to manyof the treated dams.     

Effects of flutamide on puberty in male rats: an evaluation of the protocol for the assessment of pubertal development and thyroid function

To establish a test protocol for the rodent 20-d thyroid/pubertal assay, flutamide, a non-steroidal androgen antagonist, was administered to intact male Sprague-Dawley rats from postnatal d 33 for 20 d, and several reproductive endpoints were examined to assess the sensitivity of a number of parameters with respect to the detection of endocrine-related effects. Immature male rats were divided into 4 groups and given flutamide once daily by oral gavage at doses of 0, 1, 5, or 25 mg/kg/d. Prepuce separation was significantly delayed in flutamide-treated rats (5 and 25 mg/kg/d). One day after the last dose, the rats were sacrificed. Flutamide treatment resulted in a significant reduction in the weights of epididymides, ventral prostate, seminal vesicles plus coagulating glands and fluid, levator ani plus bulbocavernosus muscles, Cowper's glands, and glans penis. The weight of adrenal glands decreased at 25 mg/kg/d, while testes and any other organ weights were unaffected. No microscopic changes were observed in the thyroid glands. Serum levels of testosterone were significantly increased in the flutamide-treated groups (5 and 25 mg/ kg/d) and serum levels of estradiol were also increased (25 mg/kg/d). No differences were observed in the serum thyroxine levels. These results indicate that flutamide delays puberty in the male rat, and its mode of action appears to be via altered secretion of steroids, which subsequently affect the development of the reproductive tract. Thus, this assay might be used as an alternative for screening antiandrogenic activities of chemicals.     

Acute, Pharmacokinetic, and Subchronic Toxicological Sudies of 2,4-Dichlorophenoxyacetic Acid

The single-dose oral LD₅₀ values in Fischer 344 rats for technical-grade2,4-dichlorophenoxyacetic acid (2,4-D), es ters, and salts rangedfrom 553 mg/kg (isobutyl ester in females) to 1090 mg/kg (dimethylaminesalt in males). The LDH values for the acid, esters, or salts,when expressed as acid equivalents, were consistent which suggeststhat the acute toxicity was due to 2,4-D per se. Acute dermalLD₅₀ values in rabbits for the acid, esters, and salts weregreater than 2000 mg/kg. Overall, these results indicate thatthe acute oral and dermal toxicity of 2,4-D are low. Pharmacokineticswere evaluated in male Fischer 344 rats given single oral dosesof 10, 25, 50, 100, or ISO mg 2,4- [¹⁴CJD/kg The amount of 2,4-Din the plasma, kidney, and urine 6 hr postdosing indicated thatthe urinary elimination of 2,4-D was saturated in male ratsgiven oral doses in excess of 50 mg/ kg. Subchronic dietarystudies in male and female Fischer 344 rats used dose levelsof 0, 15, 60, 100, or 150 mg/kg/thy of purified or technical-grade2,4-D acid for 13 weeks. Body weight gains were decreased forboth sexes at the higher dose levels of purified and technical-grade2,4-D acid. Kidney weights were increased in all treated malerats and in females given the higher three dose levels of purified2,4-D. Treatment-related cytoplasmic alterations were presentin the renal proximal tubules of most rats given 60mg/kg/thyand higher of purified or technical-grade 2,4- D; a few femalesgiven 15 mg/kg/thy also had slight alterations in the cytoplasmof the proximal tubules. A dose-related degenerative changewas identified in the descending proximal renal tubules of allmale rats given the highest three dose levels of either testmaterial and some given 15 mg/kg/thy. Dose levels of 100 or150 mg/kg/thy of either compound for both sexes produced minimalswelling and increased staining homogeneity in the liver cellsand were associated with a slight elevation of liver weightand serum glutamic pyruvic transaminase activity. Higher doselevels of technical-grade and purified 2,4-D decreased totalserum tetraiodothyronine levels in female rats, however, themorphology of the thyroid gland was normal. The no-observed-effectlevel (NOEL) was less than 15 mg/kg/day for both purified andtechnical-grade 2,4-D acid.     

Subacute toxicity of chitosan oligosaccharide in Sprague-Dawley rats

A subacute oral toxicity study of chitosan oligosaccharide was performed in Sprague-Dawley rats of both sexes. Each 36 male and female rats were administered by gavage with 500, 1,000 and 2,000 mg/kg/day for 4 weeks (7 days/week), respectively. Examinations regarding clinical signs, body weights, hematological and biochemical parameters, and histopathological examinations were carried out. There were no significant differences in behavior or external appearance, body weight and food consumption between control and treated rats. In addition, no significant differences in urinalysis, hematology, blood biochemistry, relative organ weights and histopathological findings were found in both control and treated rats. In conclusion, it was suggested that subacute toxicity of chitosan oligosaccharide was low and the no-observed adverse effect level was considered to be over 2,000 mg/kg in rats.     

Acute and subacute toxicity of yeast hydrolysate from Saccharomyces cerevisiae

The objective of this study was to obtain data on the safety-in-use of yeast hydrolysate in 10–30 kDa molecular weight as a dietary supplement by assessing its acute and subacute oral toxicity in female and male Sprague–Dawley (SD) rats. The single oral dose of the hydrolysate at 5000 mg/kg did not produce mortality or significant changes in the general behavior and gross appearance of the internal organs of rats. In subacute toxicity study, the hydrolysate was administered orally at a dose of 1000 mg/kg/day for a period of 14 days. The satellite group was treated with the hydrolysate at the same dose and the same period and kept for another 14 days after treatment. There were no significant differences in organ weights between control and treated group of both sexes. Hematological analysis and blood chemistry revealed no toxicity effects of Saccharomyces cerevisiae hydrolysate. Pathologically, neither gross abnormalities nor histopathological changes were observed. These results show that the hydrolysate possesses very low toxicity as indicated in SD rat model.     

Sex-dependent toxicity of a novel acyl-CoA:cholesterol acyltransferase inhibitor, YIC-C8-434, in relation to sex-specific forms of cytochrome P450 in rats.

YIC-C8-434 is a novel inhibitor of acyl coenzyme A:cholesterol acyltransferase (ACAT). To clarify the toxicity of YIC-C8-434, the compound was given orally to Sprague-Dawley rats for 28 days at 0, 4, 20, 100, or 500 mg/kg/day. The toxicity of the drug differed significantly between male and female rats. In female rats treated at 500 mg/kg, many symptoms including moribund condition, suppression of weight gain and food consumption, abnormal blood chemistry, and decreases in organ weights (thymus, ovaries, and uterus) were observed. In male rats by contrast, no significant toxicity was observed at any dose. After a single administration of YIC-C8-434 at 500 mg/kg, female rats had a higher blood concentration of the compound than male rats. Little elimination of YIC-C8-434 was observed in female rats on analysis of drug-elimination kinetics. Furthermore, the metabolism of YIC-C8-434 was analyzed using rat hepatic microsomal preparations from both sexes. Consistent with the observations in vivo, hepatic microsomes from male rats better metabolized YIC-C8-434 than those from females. In addition, the metabolism of YIC-C8-434 by hepatic microsomes from male rats was blocked by SKF525A, a P450 inhibitor. Inhibition experiments using anti-rat CYP1A1, CYP1A2, CYP2B1, CYP2C11, CYP2E1, CYP3A2, and CYP4A1 antisera indicated that CYP3A2 played the predominant role in the metabolism of YIC-C8-434 in rats. Since there is less CYP3A2 in the liver of female than male rats, the involvement of CYP3A2 in YIC-C8-434 metabolism has implications for the sex-related metabolic activity and toxicity of YIC-C8-434.     

Hypothyroidism protects di(n-butyl) phthalate-induced reproductive organs damage in Sprague-Dawley male rats

This study examined the deleterious effects of di(n-butyl) phthalate (DBP) on the male reproductive organs in hypothyroid rats. Hypothyroidism was induced in prepubertal male rats (28 days of age) by an intraperitonial (i.p.) injection of 10 mg/kg/day propylthiouracil (PTU) for 30 days. DBP (100 and 500 mg/kg/day) was administered by oral gavages to the intact or hypothyroid rats for 30 days. The body weight of the PTU-treated rats was significantly lower than the control group. The total triiodothyronine (T3) and thyroxine (T4) serum level was lower, and the thyroid-stimulating hormone (TSH) level was higher in the hypothyroid rats than in the control rats. The DBP treatment rats showed significantly lower testes, epididymides, seminal vesicles, and ventral prostate weights than the untreated rats. The hypothyroid rats had significantly higher thyroid weights and lower adrenal glands weights than the control rats. The histomorphological examination showed diffused Leydig cells hyperplasias and germ cells loss in the DBP (500 mg/kg)-treated rats, whereas these effects were mild in the DBP-treated hypothyroid rats. The serum levels of monobutyl phthalate (MBP) were significantly lower in PTU-induced hypothyroid rats than in the DBP-treated rats. This data suggests that the hypothyroid status might offer some protection from male reproductive organ toxicity caused by a disturbance in the metabolic activation of the parent compound, DBP.     

Antiulcer activity and subacute toxicity of trans-dehydrocrotonin from Croton cajucara

The antiulcerogenic activity of trans-dehydrocrotonin (DHC), a nor-clerodane diterpene isolated from Croton cajucara Benth. (Euphorbiaceae), and its subacute (35 days) toxicity were studied in mice and rats, respectively. For the antiulcerogenic tests, models of gastric ulcers induced in mice by ethanol/HCl or stress were used. In both models, an oral dose of DHC (100 mg/kg) significantly reduced (P < 0.01) the formation of gastric lesions. DHC was also tested for its ability to scavenge free radicals, but no such action was observed in rat liver mitochondria. To assess the subacute toxicity, rats were treated orally with DHC (25, 50 and 100 mg/kg) for 5 weeks. A significant increase in liver weight was observed in male and female rats at highest doses, whereas a significant reduction in plasma alkaline phosphatase and cholesterol levels and an increase in gamma glutamyl transpeptidase were observed only at the highest dose (100 mg/kg) in female rats. DHC caused histopathological alterations in the liver that included a turbid tumefaction, microvacuolar degeneration and nuclear alterations. Despite the beneficial antiulcerogenic activity of DHC, our results suggest that the long-term use of this compound may induce liver damage.     

Safety evaluation of Nostoc flagelliforme (nostocales, cyanophyceae) as a potential food

The safety of the alga genus Nostoc flagelliforme Born. etFlah. as a human food source was evaluated in an oral acute toxicity study and in a 28-day oral subacute toxicity study using rats. In the acute toxicity study, the dried powder of N. flagelliforme was orally administered to male and female rats at a dose of 1250 mg/kg and 2500 mg/kg. Neither mortality nor changes in general condition were observed in either the study groups or the control group over a 14-day observation period. In the subacute toxicity study, N. flagelliforme powder was administered orally to male and female rats at a dose of 500 mg/kg and 1000 mg/kg for a period of 28 days. Neither mortality nor changes in general condition were observed in either the treatment group or the control group throughout the 28-day administration period. No reduction in food consumption or body weight gain was observed in the experimental animals. Ophthalmological tests performed at the end of the administration period revealed no abnormalities within the ophthalmological parameters. In the haematological tests and serum biochemical tests performed at the time of completion of the administration period, no adverse effects of N. flagelliforme were observed. At autopsy, organ weight at the end of the experimental period and histopathological tests of specimens obtained from the autopsied animals revealed no significant influences of N. flagelliforme. In conclusion, considering the absence of adverse effects of N. flagelliforme in this study, findings in the oral acute toxicity study and the 28-day oral subacute toxicity study may indicate the safety of N. flagelliforme for human consumption. This study is in agreement with the novel nutraceutical idea “Phycophagism”.     

Reproductive effects in male and female rats from neonatal exposure to p-octylphenol

A number of alkylphenolic compounds are used in a variety of commercial products and have been shown in in vitro studies to be weakly estrogenic, but in vivo data are not available addressing this issue in mammals. Human exposure to alkylphenols may occur not only from these environmental contaminants but also through contact with manufactured and metabolic breakdown products. In this study, Sprague-Dawley rats were exposed to octylphenol by oral gavage at doses of 0 (vehicle: corn oil), 12.5, 25, 50, or 100 mg/kg once daily on postnatal days 1 through 5 to examine its effects on male and female reproductive function after puberty. In addition, preputial separation and vaginal opening as endpoints of sexual maturation, estrous cycling, sperm count, serum testosterone concentration, and histopathologic changes of the reproductive organs of male and female rats were examined. Male reproductive organs were weighed at necropsy. Body weights of male and female rats exposed to octylphenol at 50 and 100 mg/kg throughout the study after the administration period, those of both sexes at 7 and 9 weeks of age in the 25 mg/kg group, and that of females at 9 weeks of age in the 12.5 mg/kg group were lower than those of controls. Significant delays in acquisition of puberty in males and females exposed to octylphenol at 50 and 100 mg/kg were observed. Estrous cycle, copulation and fertility, sperm count, and serum testosterone concentration were not affected by neonatal exposure to octylphenol. Significant decrease in absolute and relative prostate weight in the 12.5, 25, 50, and 100 mg/kg groups, and absolute epididymal weight in the 100 mg/kg group, increase in relative testes weight in the 100 mg/kg group, and relative seminal vesicle weights in the 50 and 100 mg/kg groups were found. Histopathologic analyses of reproductive organs in male and female rats exposed neonatally to octylphenol revealed no marked alterations. The results of this study indicate that early neonatal exposure to octylphenol by oral gavage did not cause dysfunction of reproductive performance (mating and fertility) in male or female rats, and no disruption of development of the reproductive tract was observed in male or female rats, while significant decreases in body weights in the 25 mg/kg and more groups, delays of sexual maturation in the 50 mg/kg and greater groups, and decrease in ventral prostate weights in all octylphenol-treated groups were found. Therefore, it is concluded that NOAEL (no-observed adverse effect level) for systemic toxicity was ≤ 12.5 mg/kg/day and that for reproductive toxicity was 100 mg/kg/day under the present experimental condition.     

Toxicity of (4,4'-(isopropylidenedithio)bis(2,6-di-t-butylphenol)), probucol, in mice, rats, dogs and monkeys: demonstration of a species-specific phenomenon

Probucol (DH-581), a hypocholesterolemic chemical, was tested for acute, subacute and chronic toxicity in mice, rats, dogs and monkeys. The oral LD50 for mice and rats was found to be in excess of 5280 mg/kg. Neither clinical signs nor laboratory data indicative of toxicity were found in any of the species of animals studied although deaths without prodromal signs occurred in dogs on subacute and chronic studies. Compound-related morphologic changes were not found in tissues from the different species of animals used for the tests. The precipitous deaths in dogs, without overt clinical signs of toxicity, abnormal clinical laboratory data and postmortem lesions are considered a species-specific phenomenon. Reduction in serum cholesterol concentrations occurred in all species of animals studied.     

Subacute toxicological examination of Dithane M-45

A subacute toxicological study of the effects of the ethylene-bisdithiocarbamate-containing fungicide Dithane M-45 (80% mancozeb) was carried out in male Wistar rats. The rats were given Dithane mixed in the feed at doses of 0, 10, 50, 75, 113, 169, 253 or 379 mg/kg body weight for 12 wk. One-third of the rats given 379 mg Dithane/kg body weight died, and doses of greater than or equal to 169 mg/kg decreased the growth of the rats as well as the nutrient utilization. The relative weights of the liver and thyroid were significantly increased in rats given greater than or equal to 75 mg Dithane/kg body weight, and those of the kidneys, adrenals and testes were significantly increased in the two highest dose groups. The serum cholesterol level was increased significantly in groups given greater than or equal to 75 mg/kg, and doses of 113, 169 or 253 mg/kg caused the elevation of the triglyceride content of the liver. The two highest doses of Dithane decreased the detoxicating capacity of the liver. The function of the thyroids was impaired even by very small doses of Dithane: at a dose of 10 mg/kg body weight the quantity of iodine stored in the thyroids was decreased by 20%. At doses of greater than or equal to 50 mg/kg statistically significant decreases in thyroid iodine content were observed. Histological examination of the thyroids showed dose-dependent hyperplasia in rats treated with Dithane.