Kinetics of genistein and its conjugated metabolites in pregnant Sprague-Dawley rats following single and repeated genistein administration.

Diets high in soy-based products are well known for their estrogenic activity. Genistein, the predominant phytoestrogen present in soy, is known to interact with estrogen receptors (ER) alpha and beta and elicits reproductive effects in developing rodents. In the rat, genistein is metabolized predominantly to glucuronide and sulfate conjugates, neither of which is capable of activating ER. Therefore, it is critical to understand the delivery of free and conjugated genistein across the placenta to the fetus following maternal genistein exposure such that the potential fetal exposure to free genistein can be assessed. Genistein (4 or 40 mg/kg) was administered to pregnant Sprague-Dawley rats by oral gavage daily from gestation day (GD) 5 through 19 or on GD 19 alone. Maternal and GD 19 fetal tissues were collected 0.5, 1, 2, 4, 6, 8, 12, and 24 h following administration of the final dose on GD 19. Concentrations of genistein, genistein glucuronide, and genistein sulfate were quantitated by LC-MS/MS. In maternal plasma, genistein glucuronide was the predominant metabolite. In the fetal plasma, genistein glucuronide and genistein sulfate were the primary metabolites. Genistein levels in maternal and fetal plasma were much lower than its conjugates. The concentration of genistein in placental tissue was higher than either conjugate. Fetal concentrations of unconjugated genistein following administration of 40 mg/kg were above the EC50 for ERbeta activation. Repeated administration of 40 mg/kg genistein resulted in minor changes in genistein kinetics in the pregnant rat compared to single administration of the same dose. These data suggest that conjugated forms of genistein are not transported across the placenta. High placental concentrations of genistein indicate the placenta is a potential target organ for genistein action during gestation.     

Diisobutyl phthalate has comparable anti-androgenic effects to di-n-butyl phthalate in fetal rat testis

Phthalates are widely used as plasticizers in various consumer products and building materials. Some of the phthalates are known to interfere with male reproductive development in rats, and di-n-butyl phthalate (DBP), diethylhexyl phthalate (DEHP) and butyl benzyl phthalate (BBP) were recently banned for use in toys in the EU mainly due to their reproductive toxicity. Diisobutyl phthalate (DiBP) has similar structural and application properties as DBP, and is being used as a substitute for DBP. However, knowledge on male reproductive effects of DiBP in experimental animals is lacking. METHODS: In the current study, four groups of pregnant Wistar rats were exposed to either 0mg/kg bw/day or 600 mg/kg bw/day of DiBP from gestation day (GD) 7 to either GD 19 or GD 20/21. Male offspring was examined at GD 19 or GD 20/21 for effects on testicular testosterone production and testicular histopathology. Changes in anogenital distance (AGD) were evaluated as an indication of feminisation of males. RESULTS: Anogenital distance was statistically significantly reduced at GD 20/21 together with reductions in testicular testosterone production and testicular testosterone content. Histopathological effects (Leydig cell hyperplasia, Sertoli cell vacuolisation, central location of gonocytes and presence of multinuclear gonocytes) known for DBP and DEHP were observed in testes of DiBP-exposed animals at GD 20/21. Additionally, immunohistochemical expression of P450scc and StAR proteins in Leydig cells was reduced by DiBP. At GD 19, these effects on anogenital distance, testosterone levels and histopathology were less prominent. CONCLUSION: In this study, GD 20/21 rather than GD 19 appears to be the optimal time for investigating changes in anogenital distance, testosterone levels, and testicular histopathology. DiBP has similar testicular and developmental effects as DBP and DEHP, and although more developmental and especially postnatal studies are needed to clearly identify the reproductive effects of DiBP, this study indicates a reason for concern about the use of DiBP as a substitute for DBP.     

邻苯二甲酸二丁酯对青春期雄性大鼠的毒性研究

目的探讨邻苯二甲酸二丁酯(di-n-butyl phthalate,DBP)对青春期雄性大鼠的系统毒性。方法用DBP灌胃染毒雄性Wistar大鼠8周,剂量分别为250、5001、000 mg/(kg.d)。观察临床症状,动物体重增长,血常规,血清生化,血Zn,解剖及组织病理学等指标。通过剂量-效应关系的分析,求出基准反应(benchmark response,BMR)为10%的基准剂量(benchmark dose,BMD)及95%可信限的下限值(benchmark dose lower bound,BMDL)。结果研究发现具有剂量相关的效应终点有体重、血清尿素氮含量,血清Zn含量,睾丸系数,肾脏系数和肝脏系数,其BMDL分别为408.2,57.7,99.0,263.3,103.1,24.3 mg/(kg.d)。结论DBP对雄性青春期大鼠具有一般毒性。DBP对雄性青春期大鼠一般毒性的最低可观察毒性作用剂量水平(lowest observed adverse effect level,LOAEL)为250 mg/(kg.d),BMD和BMDL分别为42.4和24.3 mg/(kg.d)(根据肝脏系数),同时肝脏系数为最敏感效应指标。研究结果显示,BMDL评价方法较LOAEL方法更为敏感。     

Urinary and amniotic fluid levels of phthalate monoesters in rats after the oral administration of di(2-ethylhexyl) phthalate and di-n-butyl phthalate

Two studies were designed to examine amniotic fluid and maternal urine concentrations of the di(2-ethylhexyl) phthalate (DEHP) metabolite mono(2-ethylhexyl) phthalate (MEHP) and the di-n-butyl phthalate (DBP) metabolite monobutyl phthalate (MBP) after administration of DEHP and DBP during pregnancy. In the first study, pregnant Sprague-Dawley rats were administered 0, 11, 33, 100, or 300 mg DEHP/kg/day by oral gavage starting on gestational day (GD) 7. In the second study, DBP was administered by oral gavage to pregnant Sprague-Dawley rats at doses of 0, 100, or 250 mg/kg/day starting on GD 13. Maternal urine and amniotic fluid were collected and analyzed to determine the free and glucuronidated levels of MEHP and MBP. In urine, MEHP and MBP were mostly glucuronidated. By contrast, free MEHP and free MBP predominated in amniotic fluid. Statistically significant correlations were found between maternal DEHP dose and total maternal urinary MEHP (p=0.0117), and between maternal DEHP dose and total amniotic fluid MEHP levels (p=0.0021). Total maternal urinary MEHP and total amniotic fluid MEHP levels were correlated (Pearson correlation coefficient=0.968). Statistically significant differences were found in amniotic MBP levels between animals within the same DBP dose treatment group (p<0.0001) and between animals in different dose treatment groups (p<0.0001). Amniotic fluid MBP levels increased with increasing DBP doses, and high variability in maternal urinary levels of MBP between rats was observed. Although no firm conclusions could be drawn from the urinary MBP data, the MEHP results suggest that maternal urinary MEHP levels may be useful surrogate markers for fetal exposure to DEHP.     

Disposition of diiosononyl phthalate and its effects on sexual development of the male fetus following repeated dosing in pregnant rats

Pregnant Sprague-Dawley rats received 50, 250, and 500 mg/kg/day diisononyl phthalate (DiNP) from GD 12 to 19 via corn oil gavage to study the dose response for effects on fetal male rat sexual development as well as metabolite disposition in the dam and fetus. Monoisononyl phthalate (MiNP), mono(carboxy-isooctyl) phthalate (MCiOP), mono(hydroxyl-isononyl) phthalate (MHiNP), mono(oxo-isononyl) phthalate (MOiNP), and monoisononyl phthalate glucuronide (MiNP-G) were found in all measured tissues. MCiOP was the major metabolite, followed in decreasing order by MiNP, MHiNP, MOiNP, and MiNP-G. Percentage of dose absorbed decreased at 750 mg/kg/day. Testosterone concentration in the fetal testes was reduced at 250 and 750 mg/kg/day. Multinucleated germ cells were increased in the testes of rats at 250 and 750 mg/kg/day. The no observed effect level (NOEL) for this study was 50 mg/kg/day based on increased MNGs and reduced testes testosterone concentration in the fetal rat.     

Influence of di-(2-ethylhexyl)phthalate on fetal testicular development by oral administration to pregnant rats

Influence of di-(2-ethylhexyl)phthalate (DEHP) on testicular development was studied by oral administration of DEHP at doses of 500 and 1000 mg/kg/day to pregnant rats on gestational days (G) 7 to 18. Ethinyl estradiol (EE) at dose levels of 0.25 and 0.5 mg/kg/day was used as a reference substance. Each 5-6 pregnant rats were sacrificed and their fetuses were examined on G12, 14, 16, 18 and 20. Fetal deaths averaging 20-36% were observed at every examination in the group receiving 1000 mg/kg of DEHP. Increases of fetal deaths over 50% were also observed in the reference group that received 0.5 mg/kg of EE. Microscopic examination of the fetal testis in groups treated with DEHP revealed degeneration of germ cells in G16 fetuses and localized proliferation or hyperplasia of interstitial cells in G18 and 20 fetuses. Germ cells having more than two nuclei were observed in a few cases including the control testes of G14 fetuses. These multinucleated cells were observed frequently in G20 fetuses treated with DEHP. Examination of testes of naturally delivered offspring of dams treated with 1000 mg/kg of DEHP at 7 weeks of age revealed scattered atrophy or dilatation of seminiferous tubules. Another experiment was carried out to confirm the dose of DEHP affecting testicular development and spermatogenesis. DEHP was given to pregnant rats at doses of 125, 250 and 500 mg/kg/day during G7-18. Similar histopathological changes were observed in fetal testes of the group exposed to 500 and 250 mg/kg of DEHP, but not in those exposed to 125 mg/kg. In postnatal examinations, however, no abnormality was found in the testes at 5 and 10 weeks after birth in any of the treated groups. Furthermore, no abnormal findings were observed in the function of sperm, sperm counts and sperm morphology in the offspring of the group treated with DEHP during the fetal period at 10 weeks of age. Thus, 125 mg/kg/day is considered the no-observed-effect-level of DEHP on testicular development of rats by exposure in utero during the period of organogenesis.     

Pharmacokinetics of imipramine and its major metabolites in pregnant rats and their fetuses following a single dose

The pharmacokinetic profiles of imipramine (IMI) and its major active metabolites were determined in pregnant rats following an acute 30 mg/kg ip IMI dose. At timed intervals from 10 min to 18 hr, groups of five animals were sacrificed and whole blood, plasma, maternal and fetal brain, fetal liver, placental tissue, and whole fetus were retained for measurements of drug concentrations. IMI, 2-hydroxyimipramine (2-OH-IMI), and desipramine (DMI) rapidly appeared in all tissues and showed complex disposition kinetics. The 2-hydroxydesipramine (2-OH-DMI) metabolite was detectable in occasional samples. The area under the drug concentration-time curve for both IMI and DMI was more than 7-fold greater in whole fetus than in maternal plasma. Drug concentrations were greater in fetal brain than in whole fetus. The DMI concentration exceeded that of IMI in all tissues and DMI persisted in tissues longer: mean residence time for DMI in whole fetus was 21.2 hr compared to 3.5 hr for IMI. The area under the curve of DMI in fetal brain was 5.35 times greater than that of IMI. These results demonstrate that IMI and two of its major metabolites freely distribute to the rat fetus, that drug distribution within the fetus is regional, and that the major drug to which the fetal brain is exposed following maternally administered IMI is DMI. Studies of the teratogenic effects of extensively biotransformed drugs like IMI should consider the effects of active metabolites.     

The pharmacokinetics of cephalothin following single and repeated administration in man

The repeated administration of substances, which are mainly excreted by tubular secretion, can cause an increase of its own elimination. Because cephalothin is tubularly transported, it was of interest to prove, whether or not the repeated administration of therapeutic doses for 5 d produces an increases of renal elimination. Pharmacokinetic parameters show only small differences between the single and repeated dosing, caused by changes of volume of distribution. No stimulation of the carrier transport system was found. On the contrary, the renal elimination was reduced slightly after therapy for 5 d. Our results show that the present dosage recommendations are valid also for repeated administrations.     

Oxidative DNA damage in male Wistar rats exposed to di-n-butyl phthalate

Dialkyl phthalate esters are used in the plastic industry and widely distributed in the environment. Previously, it has been shown that di-n-butyl phthalate (DBP) produces testicular atrophy and liver enlargement in rodents, and the mechanisms behind this could involve reactive oxygen species (ROS). In this study, oxidative DNA damage was measured in terms of the premutagenic modified nucleoside 7,8-dihydro-8-oxo-2'-deoxyguanosine (8-oxodG) in nuclear DNA from liver, kidneys, and testes from rats exposed to DBP in the perinatal or preadult period. In one experiment, pregnant rats were administered 0 or 0.5 g DBP/kg/d by gavage from d 7 after conception to d 17 after delivery and organs from male offspring were analyzed. In a second experiment, 25-d-old rats were administered 0, 0.5, or 2 g DBP/kg/d by gavage for 10 d. After perinatal exposure, body and organ weights were unchanged. The 8-oxodG/10(6) dG ratio in liver DNA increased significantly in the exposed group. In contrast, the 8-oxodG/10(6) dG ratio was significantly decreased in kidney DNA, whereas it remained unchanged in the testis. After preadult exposure (postnatal d 25 to 34) the testes weight of the exposed animals were significantly decreased and severe atrophy of the seminiferous tubules was observed. The body weight of the animals in the high-dose group was significantly decreased compared to the control. The 8-oxodG levels in liver, kidney, and testis DNA remained unchanged. Although ROS has been suspected of being involved in the formation of testicular atrophy in phthalate-exposed rats, no apparent sign of oxidative DNA damage was found after phthalate exposure perinatally or during the preadult stage. With respect to phthalate-induced oxidative DNA damage in the liver, it appears that the developmental stage during exposure is important.     

Toxicokinetics of 14C-endosulfan in male Sprague-Dawley rats following oral administration of single or repeated doses

Endosulfan (ES), an organochlorine (OC) insecticide that belongs to the cyclodiene group, is one of the most commonly used pesticides to control pests in vegetables, cotton, and fruits. The toxicokinetics of 14C-endosulfan following oral administration of a single dose of 5 mg/kg body weight was investigated in male Sprague-Dawley rats. Three rats were sacrificed 30 min, 1 h, 2 h, 4 h, and 8 h after dosing. 14C-endosulfan radioactivity was detected in all tissues at each time point. In a separate experiment urine and feces were collected for 96 h. The total radioactivity recovered in the excreta for 4 days was 106.8% +/- 26.2%, with fecal elimination the major route of elimination route (94.4% +/- 21.4%). The cumulative excretion in the urine for 4 days was 12.4% +/- 4.8%. Radioactivity 8 h after administration was highest in gastrointestinal (GI) tract tissue (20.28 +/- 16.35 mg ES eq./L) and lowest in muscle (0.18 +/- 0.06 mg ES eq./L). The toxicokinetic parameters obtained from 14C-endosulfan-derived radioactivity in blood were distribution half-life (T1/2 x) = 31 min and terminal elimination half-life (T1/2 y) = 193 h. Blood concentration reached its maximum (Cmax) of 0.36 +/- 0.08 mg ES eq./L 2 h after the oral dose. Endosulfan was rapidly absorbed into the GI tract in rats, with an absorption rate constant (ka) of 3.07 h(-1).     

Molecular and toxicologic research in newborn hypospadiac male rats following in utero exposure to di-n-butyl phthalate (DBP)

The objective of this study was to first evaluate the developmental abnormalities and carry out the molecular analysis of external genitalia in newborn hypospadiac male rats induced by maternal exposure to di-n-butyl phthalate (DBP). Timed-pregnant rats were given DBP by gastric intubation at dose of 750 mg/kg body weight (bw)/day from gestation day (GD) 14 to GD18 to establish a hypospadiac rat model. The incidence of hypospadias was 46.67% in male offsprings. On postnatal day (PND) 7, at the newborn stage, decreased body weight and anogenital distance (AGD)/body weight ratio were observed in newborn hypospadiac male rats. The general image and transverse serial histological analysis of genitalia of newborn hypospadiac male rats confirmed the malformation. Autopsy analysis revealed development of reproductive organs (testes, genital tubercle (GT)), hollow organs (stomach, bladder), and solid organs (brain, heart, liver, spleen, lung, kidney, pancreas) in newborn hypospadiac male rats affected by DBP. Moreover, significantly decreased gene expression of important signaling molecules necessary for GT formation including sonic hedgehog signaling molecules (Shh and Ptched 1), bone morphogenetic proteins signaling molecules (Bmp4 and Bmp7), fibroblast growth factor signaling molecules (Fgf8, Fgf10 and Fgfr2), and the transforming growth factor-β superfamily signaling molecules (TGF-β1 and TGF-β receptor III) were observed, for the first time, in the GT of newborn hypospadias induced by DBP. These results showed that the reproductive system and development conditions of newborn hypospadiac rats were damaged by DBP. These disturbed signaling pathways which orchestrating genital development might play an important role in the toxic process of DBP induced hypospadias.     

Urinary metabolites of di-n-octyl phthalate in rats

Di-n-octyl phthalate (DnOP) is a plasticizer used in polyvinyl chloride plastics, cellulose esters, and polystyrene resins. The metabolism of DnOP results in the hydrolysis of one ester linkage to produce mono-n-octyl phthalate (MnOP), which subsequently metabolizes to form oxidative metabolites. We investigated the toxicokinetics of DnOP in adult female Sprague–Dawley rats by monitoring the excretion of DnOP metabolites in urine after oral administration of DnOP (300 mg/kg). By using authentic standards, the presence of urinary phthalic acid (PA), MnOP, and the major DnOP metabolite, mono-(3-carboxypropyl) phthalate (MCPP) was clearly established. Furthermore, we identified five additional urinary DnOP oxidative metabolites based on their chromatographic behavior and mass spectrometric fragmentation pattern. These DnOP oxidative metabolites, are postulated to be mono-carboxymethyl phthalate (MCMP), mono-(5-carboxy-n-pentyl) phthalate (MCPeP), mono-(7-carboxy-n-heptyl) phthalate (MCHpP), and isomers of mono-hydroxy-n-octyl phthalate (MHOP) (e.g., mono-(7-hydroxy-n-octyl) phthalate) and of mono-oxo-n-octyl phthalate (MOOP) (e.g., mono-(7-oxo-n-octyl) phthalate). The urinary excretion of DnOP metabolites followed a biphasic excretion pattern. The metabolite levels decreased significantly after the first day of DnOP administration although MCPP, MCHpP, MHOP, and MOOP were detectable after 4 days. We also studied the in vitro metabolism of DnOP and MnOP by rat liver microsomes. DnOP produced MnOP, MHOP, and PA in vitro whereas, MnOP produced MHOP and PA in vitro at detectable levels.     

Neurotoxicity and toxicokinetics of artelinic acid following repeated oral administration in rats

Neurotoxicity secondary to oil-soluble artemisinins has been reported in various animal species. The onset of neurotoxicity and toxicokinetics of oral artelinic acid (AL), a water-soluble artemisinin, were investigated. After dose range study, rats were dosed at either 160 mg/kg daily for 9 consecutive days or at 288 mg/kg once every other day for five doses, so that the total dose (1440 mg/kg) and duration (9 days) were identical. Neuronal damage of varying severity was identified beginning as early as 1 day after completing dosing and continued for up to 10 days post dosing. Neuronal injury was most severe 7 days after the last treatment in each of the two dosing regimens. The rats dosed with 160 mg/kg of AL daily showed moderate neurotoxicity and lost 22% of their body weight during treatment. Compared with the first dose, the toxicokinetic profile of this regimen changed significantly, with the elimination half-life increasing 3.82-fold and the volume of distribution increasing 5.23-fold on the last day of dosing. In the animals treated with AL at 288 mg/kg every other day for 5 doses, minimal neuronal degeneration (severity score 1.17) was identified and the body weight was only 8% loss. Furthermore, there were no obvious differences in the pharmacokinetic parameters between first and last dosing days with this regimen. Additionally, a progressively drug retention in stomach and drug accretion in blood were only found in rats treated with 160 mg/kg daily for 9 days. These results imply that delayed gastric emptying resulted in AL accumulation in blood and prolonged a neurotoxic exposure time (186 h) in 160 mg/kg rats when compared to that (75 h) in 288 mg/kg animals. Therefore, the drug exposure time is a key factor in the neurotoxicity induced by AL.     

Mechanism of testicular atrophy induced by di-n-butyl phthalate in rats. Part 1

Repeated oral doses of di-n-butyl phthalate (DBP) to male rats caused a decrease in testicular fructose and glucose and a sloughing of the germ cells on the first day of treatment. On day 2, more severe sloughing was seen and was accompanied by decreases in testicular iron and zinc levels and increases in the level of inositol and cholesterols. The sloughing was followed by atrophy, accompanied by dissociation of the germ cells from the Sertoli cells and reduction of triglycerides, cholesterols and phospholipids containing choline and ethanolamine residues in the testis.     

Kinetics of metapramine and its demethylated metabolites after single and chronic oral administration in man

The kinetics of metapramine and two of its demethylated metabolites were determined in six normal subjects after oral administration of a single 150 mg dose on day 1 and 3 X 50 mg dose on day 2-6. This study has shown that three demethylated metabolites are found in plasma beside metapramine. The monodemethylated metabolite I appeared to be the predominant one and the mean area under the plasma concentration curve (AUCo24) was 49% of the metapramine value. Its half-life was shorter (5.92 h) than that of metapramine (8.29 h). The kinetic profiles of metapramine and its major metabolites I and II were similar and data over 24 h could be fitted by a tri-exponential equation even though entero-hepatic cycles were observed. A high interindividual variability of data was found for both metapramine and its metabolites. There were no significant differences between men and women. The minimal plasma level (Cmin) seemed in agreement with the half-life of the drug.     

Pharmacokinetics of dextromethorphan and its metabolites in horses following a single oral administration

Dextromethorphan is an N‐methyl‐D‐aspartate (NMDA) non‐competitive antagonist commonly used in human medicine as an antitussive. Dextromethorphan is metabolized in humans by cytochrome P450 2D6 into dextrorphan, which is reported to be more potent than the parent compound. The goal of this study is to describe the metabolism of and determine the pharmacokinetics of dextromethorphan and its major metabolites following oral administration to horses. A total of 23 horses received a single oral dose of 2 mg/kg. Blood samples were collected at time 0 and at various times up to 96 h post drug administration. Urine samples were collected from 12 horses up to 120 h post administration. Plasma and urine samples were analyzed using liquid chromatography‐mass spectrometry, and the resulting data analyzed using non‐compartmental analysis. The C_max, T_max, and the t_1/2 of dextromethorphan were 519.4 ng/mL, 0.55 h, and 12.4 h respectively. The area under the curve of dextromethorphan, free dextrorphan, and conjugated dextrorphan were 563.8, 2.19, and 6,691 h*ng/mL respectively. In addition to free and glucuronidated dextrorphan, several additional glucuronide metabolites were identified in plasma, including hydroxyl‐desmethyl dextrorphan, desmethyl dextrorphan, and three forms of hydroxylated dextrorphan. Dextromethorphan was found to be eliminated from the urine predominately as the O‐demethylated metabolite, dextrorphan. Several additional metabolites including several novel hydroxy‐dextrorphan metabolites were also detected in the urine in both free and glucuronidated forms. No significant undesirable behavioural effects were noted throughout the duration of the study. Copyright © 2016 John Wiley & Sons, Ltd.     

邻苯二甲酸二丁酯阻断Shh信号通路导致尿道下裂的作用机制

目的 研究邻苯二甲酸二丁酯(DBP)孕晚期染毒诱导雄性胎鼠发生尿道下裂的作用机制.方法 雌鼠怀孕(GD)第14～18天,实验组和对照组分别予DBP 750 mg/kg、大豆油灌胃.在GD 19 d,解剖孕鼠取出胎鼠,鉴别出实验组中发生尿道下裂和未发生尿道下裂的雄性胎鼠及对照组中的雄性胎鼠,分为尿道下裂组、非尿道下裂组和对照组.用实时定量逆转录聚合酶链反应方法 检测胎鼠生殖结节(GT)中Shh(sonic hedgehog)和骨形态发生蛋白4(Bmp4)mRNA相对表达水平.结果 尿道下裂组、非尿道下裂组和对照组Shh mRNA相对表达水平分别为0.27±0.13、0.66±0.41和0.85±0.19,Bmp4 mRNA相对表达水平分别为0.18±0.05、0.40±0.25和1.00±0.44.Shh mRNA在尿道下裂组的表达较非尿道下裂组和对照组降低(P＜0.05),Bmp4 mRNA在尿道下裂组和非尿道下裂组的表达较对照组降低(P＜0.05).结论 DBP通过对GT生长发育早期Shh信号系统中部分作用因子发生作用而影响GT的生长发育,导致尿道下裂的发生.     

Urinary excretion of metabolites following a single dermal dose of [14C]methyl parathion in pregnant rats

The identification and kinetics of urinary excretion of metabolites of uniformly phenyl-labeled O,O-dimethyl O-4-nitrophenyl phosphorothioate ([¹⁴C]methyl parathion) were carried out following a single dermal dose of 10.0 mg (10 μCi)/kg in pregnant Sprague–Dawley rats at 14–18 days of gestation. Urine was collected at each time interval of 1, 2, 4, 12, 24, 48, 72, and 96 h after dosing. Total p-nitrophenol in the conjugated and non-conjugated metabolites was measured as a marker of methyl parathion exposure. Elimination of radioactivity in the urine was rapid. Of the total ¹⁴C urinary excretion, 30% of the dose was excreted within 4 h, while 50 and 90% of the dose were recovered in the urine by 24 and 96 h, respectively. Excretion rate of total radioactivity was 60 μg methyl parathion equivalent/h (1.4 mg/day). By the end of the 96-h experiment, conjugated and non-conjugated metabolites accounted for 78.1 and 21.9%, respectively. Of the non-conjugated metabolites, p-nitrophenol and O,O-dimethyl O-4-nitrophenyl phosphate (methyl paraoxon) were identified by high performance liquid chromatography (HPLC) that accounted for 20%, and 1.9% of total urinary excretion, respectively. Appearance and disappearance rate constants of p-nitrophenol in urine were 0.12 and 0.048 μg/h, respectively. Conjugated metabolites were classified as: glucuronides 12% of urinary excretion, sulfates 3%, hot sulfuric acid hydrolysable residues 47% and 16.1% remained as unidentified water soluble metabolites. Direct hot acid hydrolysis of urine yielded 49% of extractable ¹⁴C-radioactivity compared to 62% when hot acid hydrolysis followed the enzymatic hydrolysis. The presence of the conjugated metabolites as the major class of metabolites of the total excretion indicates that determining only unbound p-nitrophenol as a biological marker for methyl parathion exposure underestimates total urinary excretion of p-nitrophenol. Sequential enzymatic and acid hydrolyses of urine prior solvent extraction are necessary for complete recovery of p-nitrophenol. The results indicate that the present method would show that the pregnant field worker or a housewife being at a greater risk than previously thought.     

Effect of repeated administration of antidepressant drugs on the serum and brain concentration of testosterone and its metabolites

A repeated oral treatment (twice daily, for 21 consecutive days) with 10 mg/kg of antidepressants imipramine, amitriptyline, citalopram, mianserin affects the level of testosterone and its metabolites (5 alpha-dihydrotestosterone and estradiol-17 beta) in the serum and brain structures (cerebral cortex, hypothalamus). Citalopram and mianserin increased significantly the serum testosterone concentration, while imipramine and amitriptyline reduced the concentration of 5 alpha-dihydrotestosterone. In the cerebral cortex a reduction in 5 alpha-dihydrotestosterone after imipramine, and in the hypothalamus a decrease in testosterone level after amitriptyline were observed. None of the investigated drugs influenced estradiol-17 beta concentration in the serum or in the brain.     

Pharmacokinetics of stobadin and of the sum of its metabolites in rats during repeated administration

Stobadin dihydrochloride was administered p.o. to rats at a dose of 1 mg kg-1 once daily for 25 consecutive days. The peak and trough concentrations of the sum of stobadin metabolites, determined from Days 6-16 of treatment, demonstrated a steady-state. The mean daily excretion of 3H-radioactivity during this period was 43 per cent and 52 per cent of the administered dose into urine and faeces, respectively. The terminal half-life of stobadin in plasma following a 25-day chronic treatment was 78.3 min, which was shorter than the value of 95.3 min, determined in a single dose experiment. The data indicate that no accumulation of stobadin and of its labelled metabolites occurs in the course of repeated administration of 3H-stobadin.