Biomedical subjects

J W Laskey

Publications and source records attributed to J W Laskey.

44 records · Page 3Linked to original sources

PubMedDate not supplied

Effects of in vitro cadmium exposure on ovarian steroidogenesis in rats.

The purpose of this study was to evaluate the direct effect(s) of in vitro cadmium (Cd) exposure on steroidogenesis in rat ovaries during different reproductive states. Sprague-Dawley rats were killed on the day of proestrus, or on gestation day 6 or 16. Ovaries were removed, placed in medium and minced. Culture from each ovary was incubated with Cd2+ ions in concentrations of 0, 100, 500, 1000, 1500, or 2000 microM. One-hour whole-ovary production of progesterone (P4), testosterone and estradiol (E2) in culture medium was evaluated in the absence and presence of human chorionic gonadotropin (hCG) or hCG plus pregnenolone by specific radioimmunoassay. Under in vitro Cd exposure the most affected were productions of P4 and testosterone in proestrus rats and less in pregnant dams, whereas E2 was not affected at all. Cadmium appears to interfere with the ovarian steroidogenic pathway in rats at more than one site.

Animals↗

PubMedDate not supplied

Altered steroidogenesis in whole-ovary and adrenal culture in cycling rats.

Cultures of minced, whole-ovary (whole-ovary culture) were used to determine if three selected chemicals altered steroidogenic profiles. First, phenolsulfonthalein (PST), when used in culture medium, was tested for its influence on in vitro steroidogenesis. Next, aminoglutethimide (AGTP; 0 or 150 mg/kg once) and di(2-ethylhexyl)phthalate (DEHP; 0 or 1500 mg/kg/day for 10 days) were administered in vivo to young adult cycling rats, and the ovaries and adrenals were removed and cultured for 1 h. Ovarian steroidogenic profiles of progesterone (P), testosterone (T), and estradiol (E) release into the medium were measured using radioimmunoassay techniques. PST in medium significantly decreased ovarian P production and altered T and E production so that the T/E ratio was significantly altered. Therefore, PST was excluded in the later studies. DEHP altered steroid profiles so that proestrus appeared to be delayed. AGTP decreased P and E production significantly, and T production was increased slightly in proestrus ovaries. These AGTP alterations in T and E resulted in a highly significant increase in the T/E ratio. Adrenals from the DEHP and AGTP experiments were also cultured for 1 h, and P was assayed in the medium. AGTP, but not DEHP, significantly increased the production of P in adrenals. Whole-ovary culture is recommended as an in vitro test for chemicals suspected of interfering with steroidogenesis in vivo. This test model should be placed strategically between in vivo studies of reproductive toxicity and complex in vitro mechanistic studies.

Adrenal Glands↗

PubMedDate not supplied

Acute cadmium exposure and ovarian steroidogenesis in cycling and pregnant rats.

The purpose of this study was to evaluate the effect(s) of acute in vivo cadmium (Cd) exposure on steroidogenesis in rat ovaries during different reproductive states. Sprague-Dawley rats were injected subcutaneously on the day of diestrus, or on day 7 or 16 of gestation with a single dose of 0, 3, or 5 mg Cd/kg bw, and evaluated 24 h later. Serum progesterone and estradiol concentrations were determined. Whole-ovary culture was used to evaluate Cd effects on the production of progesterone, testosterone, and estradiol. Liver, kidney, spleen, ovary, placenta, and blood were analyzed for Cd and iron (Fe) concentrations. No general toxic effects, no disruption of estrous cyclicity, and no change in fetal viability were seen. Histologic evaluation revealed moderate Cd-related thecal congestion in ovaries of pregnant rats. The highest Cd concentrations, except for liver, were found in the fetal portion of the placenta. Interestingly, Cd-related decreases in Fe concentration were found in several tissues from rats in proestrus and on gestation day 8, and in fetal placenta from rats on gestation day 17. Cadmium appears to interfere with normal steroidogenesis at a number of sites in the biosynthetic pathway with serum estradiol concentration and ovarian estradiol production the most affected. Acute Cd effects on steroidogenesis are most severe in rats evaluated in proestrus or in early pregnancy, while in late pregnancy steroidogenesis is relatively unaffected.

Animals↗

PubMedDate not supplied

The use of cultured ovarian fragments to assess toxicant alterations in steroidogenesis in the Sprague-Dawley rat.

This study was conducted to determine the utility of using steroid production by cultured ovarian fragments to assess toxicant-induced alterations in ovarian steroidogenesis in Sprague-Dawley rats. To this end, serum steroid concentration and steroid production (progesterone (P4), testosterone (T), estradiol (E2)) by cultured ovarian fragments is described during a normal 4-day estrous cycle. This culture system was then used to profile the effects of aminoglutethimide shown to have two sites of steroidogenic inhibition, side chain cleavage enzyme and aromatase. LH, FSH, P4, and E2 concentrations in serum during the 4-day estrous cycle confirmed that described in the literature for untreated rats. All of the steroids measured had peak production levels during proestrus. The patterns of P4 and E2 production by the ovaries in an unstimulated culture mimics that seen in serum. Stimulation with hCG (100 mIU/mL) after the initial 1 h culture tends to even out the production of P4, while T production rises faster and peaks earlier. The pattern and levels of estradiol production in hCG-stimulated cultures are very similar to those in the unstimulated culture, both in pattern and in production levels. When cultured ovarian fragments from proestrous rats were treated in vitro with aminoglutethimide (1 to 16 microM), the pattern of steroid production that characterized the inhibitory effects were similar to those reported in the literature using isolated cell culture procedures. This pattern showed a rapid decrease in E2 production (IC50 of 2.43 microM), a concurrent rise in T production, and a decrease in P4 production (IC50 of 15.5 microM). This culture system is an appropriate system to rapidly assess toxicant effects on ovarian steroidogenesis following in vivo or in vitro exposure.

Aminoglutethimide↗

PubMedDate not supplied

Placental cadmium and progesterone concentrations in cigarette smokers.

Cadmium and progesterone concentrations were evaluated in term placentas collected from 56 healthy parturients in the city of Zagreb. Concentrations of lead, iron, zinc, and copper in placentas were analyzed. Data collected by questionnaire identified 29 nonsmoking and 27 smoking women. From each placenta, three samples from different locations were taken. Metals were measured by atomic absorption spectrometry. Progesterone was determined by specific radioimmunoassay in homogenized and lyophilized tissue samples after steroid extraction with ethanol. No effect of sample location was found. In placentas of smoking women an increase in cadmium, reduced progesterone and a decrease in iron concentrations were found. Placental copper and zinc concentrations were not altered. In conclusion, the results present new evidence that maternal smoking reduces placental progesterone content and support the established association of smoking with placental cadmium.

Adult↗

PubMedDate not supplied

Spermotoxicity and tissue accumulation of chlordecone (Kepone) in male rats.

Adult male rats were fed diets containing 0, 5, 15, and 30 ppm chlordecone for 90 d and then either bred to untreated females or sacrificed for terminal studies. Chlordecone residues in liver, fat, and serum were determined in the treated males. Reproductive performance was unaffected, and no histologic changes in the male sex organs could be attributed to chlordecone treatment. Reversible decreases in the motility and viability of epididymal spermatozoa and decreased sperm reserves in the cauda epididymidis were observed in rats fed 15 or 30 ppm. No effect on sperm morphology or on sperm concentration in epididymal fluid was detected. Chlordecone accumulation in tissues was linearly related to dietary levels, with the highest chlordecone concentration occurring in the liver.

Adipose Tissue↗

PubMedDate not supplied

The ethane dimethanesulfonate-induced decrease in the fertilizing ability of cauda epididymal sperm is independent of the testis.

Several decades ago it was reported that when adult male rats were exposed to a single injection of 50 mg/kg body weight ethane dimethanesulfonate (EDS) and mated with untreated females, average litter size was significantly reduced as early as 2 weeks later. Recently, we demonstrated that EDS exerts multiple effects in the epididymis of adult rats. Some of these effects were independent of reduced serum testosterone (T) levels. Later we found that EDS has direct effects on epididymal epithelial cells in vitro. Herein, we sought to determine whether EDS perturbs the fertilizing ability of cauda epididymal sperm. Four days after exposure to 50 mg/kg EDS, sperm from the proximal cauda epididymidis were inseminated into adult receptive females in utero; on the next day the percentage of fertilized eggs was determined. Exogenous T administration and castration were used to determine what role, if any, androgen deprivation and the testis had on the fertilizing ability of proximal cauda epididymal sperm. Sperm motion parameters, serum T, T in the caput/corpus epididymidis, and detergent-extracted sperm protein were evaluated and correlated with fertilizing ability. We found that both castration and EDS exposure significantly compromised the fertilizing ability of sperm in proximal cauda epididymidis 4 days after exposure. Exogenous T, sufficient to maintain serum T, completely restored the fertilizing ability of sperm following castration, but not after EDS exposure. Moreover, exogenous T failed to restore fertilizing ability when castrated animals were exposed to EDS. Thus, the effects that EDS exerts on sperm maturation in vivo are independent of the testis. Finally, the only endpoint that was well correlated with fertilizing ability was the relative amount of an acidic 18-kDa sperm protein.

Animals↗

PubMedDate not supplied

Discriminant analysis indicates a single sperm protein (SP22) is predictive of fertility following exposure to epididymal toxicants.

In a previous study, we found that ethane dimethanesulphonate (EDS) compromised the fertilizing ability of proximal cauda epididymal sperm from the rat within 4 days of exposure, an effect that persisted in castrated, testosterone (T)-implanted animals, establishing direct action on the epididymis. This EDS-induced reduction in fertilizing ability was highly correlated with a quantitative decrease in specific sperm protein. Here we sought to determine whether the fertility of proximal cauda epididymal sperm recovered from animals exposed to a variety of male reproductive toxicants could be predicted by assessing quantitative changes in specific sperm protein(s), or whether more common endpoints (e.g., sperm motility, sperm morphology, serum and epididymal tissue T, cauda epididymal sperm reserves) also are required to predict fertility. Intact adult male rats were dosed with EDS (25 or 50 mg/kg), chloroethylmethanesulphonate (CEMS; 12.5 or 18.75 mg/kg), or epichlorohydrin (EPI; 3 or 6 mg/kg) daily for 4 days. Castrated, T-implanted rats were dosed with hydroxyflutamide (HFLUT; 12.5 or 25 mg/kg) daily for 5 days. On day 5, proximal cauda epididymal sperm were inseminated in utero into receptive, cervically stimulated adult females, and on day 9, fertility (implants/corpora lutea) was assessed. Fertility-was decreased by the higher dose of each toxicant (P < 0.05) and also by the lower dose of EPI and HFLUT. Likewise, an acidic 22 kDa sperm protein (SP22) was decreased quantitatively (P < 0.05) in silver-stained two-dimensional gels by the higher dose of each toxicant as well as by the lower dose of EPI and HFLUT. Although sperm motility and serum T were altered by specific exposures, these endpoints were not useful in predicting fertility. In contrast, SP22 was highly correlated (P < 0.0001; r2 = 0.83) with fertility. Indeed, the amount of SP22 correctly predicted 90% and 94% of the fertile (> 50% fertility) and subfertile (< 50 fertility) animals, respectively, when discriminant analysis was performed. Thus, the amount of SP22 in a cauda epididymal sperm sample may be a useful predictor of fertility in toxicant-treated animals.

Animals↗