Inhibition of the first ovulation and ovarian prostaglandin F2 alpha metabolism by danazol in rats.

The present study was conducted to investigate the mode of action of danazol by monitoring the first ovulation, serum luteinizing hormone (LH) levels and ovarian prostaglandin (PG) F2 alpha metabolism in pregnant mare serum gonadotropin (PMSG)-primed immature female rats. When danazol (750 mg/kg) was given p.o. once a day for 5 days (day 24-28), the occurrence of the first ovulation, the increase in capacity to form 13,14-dihydro-PGF2 alpha and PGF2 alpha levels induced by PMSG (5 IU) injected on day 26 were clearly inhibited on day 29. Danazol also markedly suppressed the LH surge occurring on day 28. Although the danazol-induced blockage of ovulation was restored by injection of human chorionic gonadotropin, the number of oocytes was significantly decreased as compared with that of controls. The present data indicate that the inhibitory actions of danazol on ovulation and ovarian PGF2 alpha metabolism may occur via some direct effects on the ovary in addition to the suppression of gonadotropin release from the pituitary gland.     

Concentration dependency in lead-inhibited steroidogenesis in MA-10 mouse Leydig tumor cells

Lead acetate (Pb) decreases the expression of steroidogenic acute regulatory (StAR) protein and the enzymatic activities of cytochrome P-450 side-chain cleavage (P450scc) and 3beta-hydroxysteroid dehydrogenase (3beta-HSD) in a concentration-dependent manner in Leydig cells at 2 h, the duration of submaximal inhibition. This study was undertaken at 3 h of Pb incubation to compare the effects at maximal metal inhibition of steroidogenesis. Quantitatively a 3-h Pb incubation with MA-10 cells resulted in higher decreases in human chorionic gonadotropin (hCG)-stimulated progesterone production, expression of StAR protein, and the activity of 3beta-HSD compared to 2 h. In contrast, lead inhibited dibutyryl cAMP (dbcAMP)-stimulated progesterone production but lacked this effect at 2 h. Surprisingly, Pb at 3 h of incubation did not affect P450scc enzyme activity, yet this enzymatic activity was inhibited at 2 h. Data indicate that incubation time is a factor in Pb-induced alterations in MA- 10 cell steroidogenesis.     

Acute effects of lead on the renal handling of zinc in dogs

Urinary zinc excretion was monitored in anesthetized dogs before and during 4 hr after acute exposure to lead (doses: 0.3 mg Pb (as acetate)/kg as iv prime, followed by infusion of 0.057 mg Pb/min; 3mg Pb/kg, followed by 0.57 mg Pb/min as infusion; or equimolar sodium acetate in the control group). Zinc excretion in time controls was relatively constant over the 4 hr, but it rose above baseline values an average of 140 ng/min in 0.3 mg Pb/kg injected animals, and an average of 300 ng/min in 3 mg Pb/kg injected animals. Other indices of renal function, including excretion of protein, Na, K, and Mg, were relatively constant. Plasma Zn concentration was stable in time control and low Pb-administered animals, but rose significantly after the higher Pb dose. Clearance experiments using ⁶⁵Zn and in vitro ultrafiltration of plasma were performed in another series of dogs under antidiuretic conditions. Zn excretion (monitored by ⁶⁵Zn) was sevenfold higher in Pb-treated dogs; plasma Zn concentration was slightly, but not significantly, elevated. Ultrafiltrable Zn concentration was 2.5-fold higher and fractional Zn excretion was three times higher in Pb-treated dogs. The stop-flow pattern for Zn after Pb treatment showed no change in the distal tubular handling of Zn, but revealed prominent net proximal tubular secretion of Zn in all animals, a frequency statistically different from that observed in control animals. Thus, acute Pb treatment in dogs produced an increase in urinary Zn excretion which was related both to an increase in ultrafilterable plasma Zn and a change in renal tubular Zn transport. The plasma concentrations of insulin and glucagon were not altered by lead.     

Indomethacin inhibits the secretion of inhibin and oestradiol-17 beta stimulated by pregnant mare serum gonadotrophin in the immature female rat.

The involvement of prostaglandins (PGs) in the regulation of inhibin and oestradiol-17 beta secretion from the ovary was studied by determining the effects of indomethacin and/or pregnant mare serum gonadotrophin (PMSG) on the levels of ovarian hormones in immature female rats. An increase in serum and ovarian levels of inhibin and oestradiol-17 beta was observed with a reciprocal reduction in serum follicle-stimulating hormone (FSH) levels from within 26 to 50 h after a single injection of 5 IU PMSG (s.c.) when the rats were 26 days of age. Administration of indomethacin to suppress PGs synthesis, simultaneously with PMSG, resulted in a substantial reduction in the levels of ovarian PGF2 alpha and serum inhibin and oestradiol-17 beta, which were both enhanced by PMSG treatment, 24 h after treatment with drugs. Indomethacin also reduced the basal serum level of inhibin. In the indomethacin-treated animals, the serum level of FSH was significantly increased regardless of the treatment with PMSG, indicating that the negative feedback regulation between FSH and inhibin is operating in these animals. These results demonstrate the inhibitory effects of indomethacin on PMSG-enhanced inhibin and oestradiol-17 beta production, suggesting that PGs play a regulatory role in the secretion of inhibin and oestradiol-17 beta from the gonadotrophin-stimulated ovary.     

Gonadotropin regulation of glutathione synthesis in the rat ovary.

Glutathione (GSH), an antioxidant and conjugator of electrophilic toxicants, prevents toxicant-mediated destruction of ovarian follicles and oocytes. Ovarian GSH has previously been shown to change with estrous cycle stage in rats, suggesting that the gonadotropin hormones may regulate ovarian GSH synthesis. The present studies tested the hypotheses that [1] estrous cycle-related changes in ovarian GSH result from cyclic changes in protein and mRNA expression of the rate-limiting enzyme in GSH synthesis, glutamate cysteine ligase (GCL, also called gamma-glutamylcysteine synthetase), and [2] that these changes result from gonadotropin-mediated regulation of GCL subunit expression. In the first experiment, ovaries were harvested from cycling adult female rats on each stage of the estrous cycle. In the second experiment immature female rats were injected with pregnant mare's serum gonadotropin (PMSG) to stimulate follicular development or with vehicle and killed 8, 24, or 48 h later. In both experiments the ovaries were harvested for [1] total GSH assay, [2] Western analysis for GCL catalytic (GCLc) and regulatory (GCLm) subunit protein levels, or [3] Northern analysis for Gclc and Gclm mRNA levels. Ovarian GSH concentrations and Gclc and Gclm mRNA levels, but not GCL subunit protein levels, varied significantly with estrous cycle stage. PMSG administration significantly increased ovarian GSH concentrations 24 and 48 h later. GCLm protein levels increased significantly at 24 h and 48 h following PMSG. GCLc protein levels did not increase significantly following PMSG. Gcl subunit mRNA levels were not significantly increased at any time point by the planned ANOVA; however, an increase in Gelc at 48 h was identified by t-testing. These results support the hypothesis that gonadotropins regulate ovarian GSH synthesis by modulating GCL subunit expression.     

Trichosanthin induces atresia of ovarian follicles and inhibits steroidogenesis in gonadotropin-primed immature mice.

1. Immature mice were induced to ovulate by injections of pregnant mare serum gonadotropin (PMSG) and human chorionic gonadotropin spaced 48 hr apart. 2. Trichosanthin (TCS), a protein purified from tubers of Trichosanthes kirilowii (Family Cucurbitaceae), was administered respectively 24 hr before, on the same day as, 24 hr after and 48 hr after the PMSG injection. 3. The results of TCS injections at different times were generally similar. The number of maturing follicles, corpora lutea and ovulated oocytes, and the ovarian weight, remained unaltered. 4. However, there was an increased incidence of follicular atresia and degeneration of ovulated oocytes, and a lowering of serum estradiol-17 beta and progesterone levels.     

Immunohistochemical localization and physiological regulation of carbonyl reductase in immature rat ovary

The present study was performed to clarify the role of the ovarian carbonyl reductase (OCR) in ovarian function in immature rats. The OCR activities towards three specific substrates, 13,14-dihydro-PGF2 alpha, 4-benzoylpyridine and menadione, were photometrically and radiochemically determined in the 9,000 x g supernatants of ovaries, and OCR content was measured by Western-blot-peroxidase anti-peroxidase (PAP) analysis. Immunohistochemical localization of the enzyme in the ovary was performed by the avidin-biotin-complex (ABC) method for paraffin sections. Positive immunoreactivity with OCR antibody was observed for the theca cells and interstitial gland cells at 72 hr after pregnant mare serum gonadotropin (PMSG) treatment when ovulation was confirmed, and the granulosa cells were consistently negatively stained. The OCR activity was significantly increased by PMSG, human chorionic gonadotropin (hCG) and PMSG-hCG treatments, but estradiol and tamoxifen overcame the effect of PMSG on the enzyme activity. Moreover, estradiol enhanced the effect of hCG, but tamoxifen did not. Changes in the OCR activity well-correlated with those in the OCR content. These findings indicate that the OCR is regulated by gonadotropin and estrogen and that metabolites formed by the enzyme could be closely involved in ovarian cell function.     

Association of alterations in energy metabolism with lead-induced delays in rat cerebral cortical development

Fifteen day-old rat pups taken from dams exposed to 200 mg of lead (Pb) in drinking water were observed to have reduced synaptic densities in the cerebral cortex as determined by ethanol-phosphotungstic acid staining. Synaptic figures of animals in the Pb groups were also observed to possess a less mature synaptic profile.Cerebral cortical slices taken from pups of Pb-treated dams exhibited enhanced respiratory responses to a 3 to 30 mM increase in K⁺ concentration. This response was associated with a higher rate of glucose uptake by tissues of Pb-treated pups unaccompanied by a change in lactic acid output. Cerebral cortical concentrations of amino acids were not altered by Pb-treatment. Serum thyroid hormone levels were identical in 15-day old animals from the control and Pb-treated groups.These data further substantiate delayed cerebral cortical development as a result of low-level Pb exposures, and suggest that such delays may be associated with a direct effect of Pb on cerebral energy metabolism.     

Puerarin protects rat kidney from lead-induced apoptosis by modulating the PI3K/Akt/eNOS pathway

Puerarin (PU), a natural flavonoid, has been reported to have many benefits and medicinal properties. However, its protective effects against lead (Pb) induced injury in kidney have not been clarified. The aim of the present study was to investigate the effects of puerarin on renal oxidative stress and apoptosis in rats exposed to Pb. Wistar rats were exposed to lead acetate in the drinking water (500 mg Pb/l) with or without puerarin co-administration (100, 200, 300 and 400 mg PU/kg intragastrically once daily) for 75 days. Our data showed that puerarin significantly prevented Pb-induced nephrotoxicity in a dose-dependent manner, indicated by both diagnostic indicators of kidney damage (serum urea, uric acid and creatinine) and histopathological analysis. Moreover, Pb-induced profound elevation of reactive oxygen species (ROS) production and oxidative stress, as evidenced by increasing of lipid peroxidation level and depleting of intracellular reduced glutathione (GSH) level in kidney, were suppressed by treatment with puerarin. Furthermore, TUNEL assay showed that Pb-induced apoptosis in rat kidney was significantly inhibited by puerarin. In exploring the underlying mechanisms of puerarin action, we found that activities of caspase-3 were markedly inhibited by the treatment of puerarin in the kidney of Pb-treated rats. Puerarin increased phosphorylated Akt, phosphorylated eNOS and NO levels in kidney, which in turn inactivated pro-apoptotic signaling events including inhibition of mitochondria cytochrome c release and restoration of the balance between pro- and anti-apoptotic Bcl-2 proteins in kidney of Pb-treated rats. In conclusion, these results suggested that the inhibition of Pb-induced apoptosis by puerarin is due at least in part to its antioxidant activity and its ability to modulate the PI3K/Akt/eNOS signaling pathway.     

Effect of 3,6-dimethylpyrazine-2-thiol on androstenedione-induced increase of uterine weight in female rats

3,6-Dimethylpyrazine-2-thiol administered at 10-70 mg/kg, p.o. was found to suppress androstenedione-induced increase of uterine weight in female rats. This action was weaker than that of aminoglutethimide (3-30 mg/kg, p.o.). After administration of androstenedione, increased plasma estradiol levels were reduced by 3,6-dimethylpyrazine-2-thiol. Moreover, in vitro, production of estradiol in the pregnant mare serum gonadotropin (PMSG)-treated ovary was inhibited by 3,6-dimethylpyrazine-2-thiol. These results suggest that 3,6-dimethylpyrazine-2-thiol has an inhibitory action on aromatase activity.     

Interactions of chronic lead exposure and intermittent stress: consequences for brain catecholamine systems and associated behaviors and HPA axis function.

Elevated lead (Pb) burden and high stress levels are co-occurring risk factors in low socioeconomic status (SES) children. Our previous work demonstrated that maternal Pb exposure can permanently alter hypothalamic-pituitary-adrenal (HPA) axis function and responsivity to stress challenges in offspring. The current study sought to determine the consequences of chronic Pb exposures initiated later in development combined with variable intermittent stress challenges. Male rats were exposed chronically from weaning to 0, 50, or 150 ppm Pb acetate drinking solutions (producing blood Pb levels of <5, 9-15, and 23-27 mug/dl, respectively). Pb itself decreased basal plasma corticosterone, with greater effects at 50 than 150 ppm; 150 ppm reduced both cytosolic and nuclear glucocorticoid receptor binding. Responsivity to stress challenges including novelty, cold, and restraint, was measured as changes in Fixed Interval (FI) schedule-controlled behavior in a subset of rats within each group. FI performance was modified by novelty stress only in Pb-treated rats, whereas cold and restraint stress effects were comparable across groups. Novelty elevated corticosterone equivalently across groups, but cold stress markedly increased corticosterone only in Pb-treated groups. The pattern of Pb-induced changes in serotonin (5-HT) or its metabolite 5-HIAA in frontal cortex, nucleus accumbens, striatum, and hypothalamus resembled that observed for basal corticosterone levels indicating a relationship between these variables. In addition to suggesting the potential for HPA axis-mediated effects of Pb on the central nervous system, these findings also raise questions about whether single chemicals studied in isolation from other relevant risk factors can adequately identify neurotoxic hazards.     

Increased β-amyloid deposition in Tg-SWDI transgenic mouse brain following in vivo lead exposure

Previous studies in humans and animals have suggested a possible association between lead (Pb) exposure and the etiology of Alzheimer's disease (AD). Animals acutely exposed to Pb display an over-expressed amyloid precursor protein (APP) and the ensuing accumulation of beta-amyloid (Aβ) in brain extracellular spaces. This study was designed to examine whether in vivo Pb exposure increased brain concentrations of Aβ, resulting in amyloid plaque deposition in brain tissues. Human Tg-SWDI APP transgenic mice, which genetically over-express amyloid plaques at age of 2–3 months, received oral gavages of 50 mg/kg Pb acetate once daily for 6 weeks; a control group of the same mouse strain received the same molar concentration of Na acetate. ELISA results revealed a significant increase of Aβ in the CSF, brain cortex and hippocampus. Immunohistochemistry displayed a detectable increase of amyloid plaques in brains of Pb-exposed animals. Neurobehavioral test using Morris water maze showed an impaired spatial learning ability in Pb-treated mice, but not in C57BL/6 wild type mice with the same age. In vitro studies further uncovered that Pb facilitated Aβ fibril formation. Moreover, the synchrotron X-ray fluorescent studies demonstrated a high level of Pb present in amyloid plaques in mice exposed to Pb in vivo. Taken together, these data indicate that Pb exposure with ensuing elevated Aβ level in mouse brains appears to be associated with the amyloid plaques formation. Pb apparently facilitates Aβ fibril formation and participates in deposition of amyloid plaques.     

Modulating effects of Korean ginseng saponins on ovarian function in immature rats

The modulating effects of Korean ginseng saponins on ovarian functions were investigated in immature rats superovulated with pregnant mare serum gonadotropin (PMSG). A single dose of 1 mg (0.1 ml/head) of Korean ginseng total saponin (GTS), Korean ginseng protopanaxatriol saponin (GPT), Korean ginseng protopanaxadiol saponin (GPD), or ginsenoside-Rb1 (Gin-Rb1) was intravenously injected via jugular vein catheter three times at 1 h (early follicular phase), 25 h (middle follicular phase), and 50 h (late follicular phase) after 30 IU PMSG administration. GPD and Gin-Rb1 significantly suppressed excessive ovulatory response caused by PMSG (p<0.05). All Korean ginseng saponins significantly improved oocyte quality by decreasing the proportion of abnormal oocytes (p<0.05). Gin-Rb1 significantly decreased preovulatory serum levels of androgens and 17beta-estradiol, while GPD increased preovulatory serum progesterone level (p<0.05). GPD significantly the increased postovulatory serum progesterone level (p<0.05). These results provide strong evidence that Korean ginseng saponins have a curative effect on ovarian dysfunction caused by excessive stimulation with PMSG.     

人体免疫球蛋白对卵巢过度刺激大鼠的治疗效应

目的 探讨静脉用人体免疫球蛋白(IVIG)对卵巢过度刺激大鼠(OHSS)的治疗作用.方法 将Wistar雌性清洁大鼠随机分成卵巢过度刺激(A)组、免疫球蛋白注射(B)组和生理盐水对照(C)组.A组皮下注射孕马血清促性腺激素(PMSG) 10IU,每日1次,连续4d,第5天皮下注射100IU人绒毛膜促性腺激素(hCG)1次,建立OHSS模型;B组在OHSS模型建立的同时,从第1天起同时腹腔注射IVIG 100mg,每天1次,连续5d.hCG注射后48h,评估血管通透性,卵巢总重量,取大鼠血、卵巢酶联免疫法测定白细胞介素(IL)-1、6、10.结果 B组的卵巢总重量、血管通透性均低于A组(P＜0.05);三组血IL-1和卵巢IL-1、10含量均不同(P＜0.05),B组卵巢IL-10含量最低(P＜0.05).结论 IVIG可降低OHSS大鼠卵巢重量和卵巢血管通透性,提示对OHSS有治疗效应.     

Hepatoprotective role of zinc in lead-treated, protein-deficient rats

The current study was designed to evaluate the hepatoprotective role of zinc after lead (Pb) treatment of protein-deficient (PD) rats. The animals were subjected to seven different treatment groups: G-1 (normal control, 18% protein), G-2 (protein-deficient, 8% protein), G-3 (Pb-treated, 100 mg/kg body weight of lead acetate), G-4 (Zn-treated, zinc sulfate at a dose level of 227 mg/L drinking water), G-5 (PD + Pb-treated), G-6 (PD + Zn-treated), and G-7 (PD + Pb + Zn-treated). Serum albumin levels and total serum protein contents were estimated to assess the severity of protein deficiency at the end of 8 weeks in all the treatment groups. Also, the study explored the role of zinc on antioxidative defense system enzymes in liver of protein-deficient rats subjected to lead toxicity treatment. Further, the study was extended to elucidate the levels of zinc and lead in liver tissue after different treatments of rats using positron-induced X-ray emission technique (PIXE). The current study indicated a significant change in the levels of various antioxidative enzymes and serum albumin as well as total protein contents of protein-deficient rats subjected to lead treatment. A significant increase in the levels of malondialdehyde (MDA), catalase, and glutathione peroxidase (GPx) was seen after 8 weeks of lead treatment of protein-deficient rats. On the contrary, levels of albumin, total protein content, superoxide dismutase (SOD), GSH, were found to be decreased. Interestingly, zinc supplementation has tended to normalize the altered levels of these enzymes to a significant extent. The levels of zinc in liver tissue was found to be decreased significantly in protein-deficient as well as lead-treated rats. However, hepatic zinc concentration was increased to a significant extent in protein-deficient rats supplemented with zinc when compared with protein-deficient rats. Further, the presence of lead was also observed in livers of lead-treated animals. In conclusion, the study revealed the antioxidative role of zinc in hepatotoxic conditions induced by subjecting the rats to protein-deficient diet and lead treatment.     

Hepatoprotective Role of Zinc in Lead-Treated,Protein-Deficient Rats

The current study was designed to evaluate the hepatoprotective role of zinc after lead (Pb) treatment of protein-deficient (PD) rats. The animals were subjected to seven different treatment groups: G-1 (normal control, 18% protein), G-2 (protein-deficient, 8% protein), G-3 (Pb-treated, 100 mg/kg body weight of lead acetate), G-4 (Zn-treated, zinc sulfate at a dose level of 227 mg/L drinking water), G-5 (PD + Pb-treated), G-6 (PD + Zn-treated), and G-7 (PD + Pb + Zn-treated). Serum albumin levels and total serum protein contents were estimated to assess the severity of protein deficiency at the end of 8 weeks in all the treatment groups. Also, the study explored the role of zinc on antioxidative defense system enzymes in liver of protein-deficient rats subjected to lead toxicity treatment. Further, the study was extended to elucidate the levels of zinc and lead in liver tissue after different treatments of rats using positron-induced X-ray emission technique (PIXE). The current study indicated a significant change in the levels of various antioxidative enzymes and serum albumin as well as total protein contents of protein-deficient rats subjected to lead treatment. A significant increase in the levels of malondialdehyde (MDA), catalase, and glutathione peroxidase (GPx) was seen after 8 weeks of lead treatment of protein-deficient rats. On the contrary, levels of albumin, total protein content, superoxide dismutase (SOD), GSH, were found to be decreased. Interestingly, zinc supplementation has tended to normalize the altered levels of these enzymes to a significant extent. The levels of zinc in liver tissue was found to be decreased significantly in protein-deficient as well as lead-treated rats. However, hepatic zinc concentration was increased to a significant extent in protein-deficient rats supplemented with zinc when compared with protein-deficient rats. Further, the presence of lead was also observed in livers of lead-treated animals. In conclusion, the study revealed the antioxidative role of zinc in hepatotoxic conditions induced by subjecting the rats to protein-deficient diet and lead treatment.     

Effect of repeated gonadotropin stimulation on ovarian reserves and proliferation of ovarian surface epithelium in mice

This study aimed to evaluate the effect of repeated ovarian stimulation (OS) on the ovarian follicular population and morphology in female mice and its influence on the embryo’s developmental ability, and the profile of the ovarian surface epithelium (OSE). A total of 75 mice were enrolled in this experiment and randomly assigned into three groups: repeated ovarian stimulated group [n = 25; receiving 5 IU pregnant mare serum gonadotrophin (PMSG) and human chorionic gonadotropin (hCG) at 6 day intervals for 5 cycles]; single ovarian stimulated group (n = 25; receiving 5 IU PMSG and hCG for 1 cycle), and control group (n = 25; without additional treatment). The follicle number at various stages and the morphologies were recorded respectively in the three groups. The harvested oocytes or embryos, cleavage rate, good quality embryo rate, and blastocyst production rate were counted and calculated, and the proliferations of ovarian surface epithelium were evaluated respectively. In the three groups, the single ovarian stimulation treatment significantly increased the mean number of ovarian oocytes or embryos (39.25±10.77 one-cell embryos/female); on the other hand, repeated gonadotropin stimulation obtained the lowest mean number (5.15± 2.81 eggs/female, P<0.01). Repeated ovarian stimulation also tended to decrease normal follicles of primary follicles (66.67%) and secondary follicles (72.86%), and got the lowest cleavage rate (67.47%), lowest good quality embryo rate (2.41%), and lowest blastocyst production rate (0). The OSE cells adjacent to the antral follicles and corpus luteum (CL) in the repeated ovarian stimulated group (81.8%) had a significantly higher proliferation rate than the other groups. The proliferation rate of the OSE in the single ovarian stimulated group (56.4%) was significantly higher than that in the control group (37.5%) (P<0.01). In conclusion, single ovarian stimulation may produce more oocytes/embryos. However, repeated gonadotropin stimulation may have a negative effect on the ovarian follicular quality, the number of mature retrieved oocytes, and the embryo quality, even increasing the chance of ovarian cancer. All authors contributed equally to this work.     

Exposure to lead during critical windows of embryonic development: differential immunotoxic outcome based on stage of exposure and gender.

Previous rat studies with lead (Pb) have shown that exposure throughout the full gestational period results in persistent immunotoxicity detectable in both juvenile and adult offspring. Gender differences are also evident. However, little is known about the persistent immunotoxic effects of Pb when administered during specific stages of embryonic development. Adult Sprague-Dawley female rats were administered Pb acetate (or control acetate) in their drinking water early in gestation (days 3-9) or late in gestation (days 15-21). Significantly depressed delayed type hypersensitivity (DTH) responses as well as elevated IL-10 production, relative monocyte numbers, and increased relative thymic weights were observed in late-gestation Pb-exposed female offspring assessed as adults. In contrast, late-gestation Pb-treated male offspring had significantly increased IL-12 production and decreased IL-10 production, while the DTH response, relative monocyte numbers and thymic weights were unchanged. With early exposure, the primary alteration was decreased nitric oxide production in Pb-treated males, whereas in Pb-treated females nitrite production was unaltered. These results suggest that at the Pb dosage employed, the embryo may be more sensitive to the full range of Pb-induced immunotoxic effects with late gestational Pb exposure, and the effects of Pb on DTH function are more pronounced in females. The data also indicate that adherent splenocytes (probably macrophages) and T lymphocytes are the primary immune cells affected during fetal Pb exposure, and that gender may influence the impact of Pb exposure on these cells. Therefore, additional developmental immunotoxicity studies are needed to examine critical windows of immune development for immunotoxicity and differential susceptibility based on gender.     

Transport of L-[125I]thyroxine by in situ perfused ovine choroid plexus: inhibition by lead exposure

Lead (Pb) exposure hinders brain development in children by mechanisms that remain unknown. Previous evidence shows that sequestration of Pb in the choroid plexus lowers the production and secretion of transthyretin (TTR), a thyroxine (T4) transport protein, from the choroid plexus into the cerebrospinal fluid (CSF). This study was undertaken to characterize the uptake kinetics of T4 by the choroid plexus and to determine if in vivo Pb exposure altered the T4 uptake in an in situ perfused ovine choroid plexus model. Sheep received i.p. injections of Pb acetate (20 mg Pb/kg) or Na acetate (as the controls) every 48 h for a period of 16 d. The [125I]T4 uptake was determined by a paired-tracer perfusion method using 0.5 microCi [125I]T4 and 2 microCi [14C]mannitol at various concentrations of unlabeled T4 (trace to 20 microM). The flux of [125I]T4 into the choroid plexus followed Michaelis-Menten kinetics with the maximum flux (Vmax) of 56.6 nmol/min/g and half-saturation constant (Km) of 10.7 mumol/L, suggesting an evident saturable influx of T4 into the choroid epithelium. In vivo Pb exposure in these sheep resulted in a significant accumulation of Pb in the choroid plexus and hippocampus. Pb treatment diminished the Vmax by 63.7% of control, but did not alter Km. The maximal cellular uptake (Umax) and net uptake (Unet) in Pb-treated animals were 2.1-fold and 1.9-fold, respectively, lower than those of control. Exposure to Pb, however, did not significantly change the flow rate through the choroid plexus. Data suggest that the choroid plexus may serve as a significant site for T4 transport into the CSF, and Pb exposure may hinder the influx of T4 from the blood into the choroid plexus.     

The effect of adrenomedullin on rats exposed to lead

Adrenomedullin (AdM) was originally discovered as a vasorelaxant peptide. The antioxidative properties of AdM have been reported recently. Through its antioxidative effect, adrenomedullin can protect organs from damage induced by stressors. Lead, commonly detected in air, soil, water and food, is a major source of oxidative stress. The effect of AdM in the liver of rats exposed to lead was investigated. Twenty-four female Wistar rats were divided into four groups: a control group (C), adrenomedullin group (AdM), lead (Pb) group and lead + adrenomedullin (Pb + AdM) group. In the Pb-treated groups, the animals were exposed to lead in drinking water containing 250 ppm PbCl2 for 4 weeks. In the AdM-treated group, the animals received an i.p. injection of AdM (3000 ng kg(-1) body weight) in the third week of lead treatment for 1 week. The activities of catalase (CAT), glutathione peroxidase (GSH-Px) and superoxide dismutase (SOD) and the level of malondialdehyde (MDA) were determined in the liver of rats. Histological changes in the liver were examined by light and electron microscopy as well. The MDA levels were increased significantly in the Pb-treated groups, but in the Pb + AdM group the MDA levels were decreased significantly when compared with the Pb group. AdM reduced hepatic damage in the Pb + AdM group, but the difference in the total histopathological scores between the Pb and Pb + AdM groups was not significant. When the results are taken together, it can be concluded that AdM may have protective or compensating effects in lead toxicity.