Follicle selection in cyclic guinea pigs with active immunization against inhibin alpha-subunit

Experiments were conducted to elucidate the mechanisms of active immunization against inhibin on ovarian follicular development and selection in guinea pigs. Estrous cycle was synchronized in experimental guinea pigs by implanting progesterone containing tubes. Antibodies that bound 125I-labeled bovine inhibin were produced by all guinea pigs receiving the inhibin vaccine (recombinant ovine alpha-subunit in oil emulsion) without any effects on duration of the estrous cycle. Active immunization against inhibin increased the plasma concentrations of progesterone during the luteal phase and the plasma concentrations of estradiol but failed to increase the plasma concentration of follicle-stimulating hormone (FSH) during preovulatory period. The treatment also increased the number of corpora lutea (from 1.3+/-0.3 to 7.0+/-1.6 per each ovary), and preovulatory sized follicles (from 1.8+/-0.6 to 7.0+/-1.6 per each ovary), and follicles stained positively for inhibin alpha-subunit (from 2.3+/-0.5 to 6.3+/-1.3 per each ovary) significantly. The results indicate that active immunization against inhibin enhances ovulation rate by affecting the follicle selection and only dominant follicle can be stained for inhibin alpha-subunit in guinea pigs. This study is firstly to provide direct evidence that inhibins play important role in follicle selections in guinea pigs.

Lack of effect of beta-naphthoflavone on induction of Nramp genes in adult rainbow trout Oncorhynchus mykiss

Natural resistance-associated macrophage protein (Nramp) genes in rainbow trout, Oncorhynchus mykiss, were identified and characterized. The greatest mRNA level encoding these genes was in the developing ovary of rainbow trout. We evaluated the response of these genes to a certain aromatic hydrocarbon receptor (AHR) agonist. Adult rainbow trout were treated with beta-naphthoflavone (BNF) (50 and 100 mg/kg) for 48 h. Using reverse-transcriptase polymerase chain reaction with ovary and head kidney RNA and specific alpha and beta Nramp primers, a 400 bp Nramp-alpha- and a 400 bp Nramp-beta-specific cDNA were obtained. There were no changes in the alpha and beta Nramp mRNA levels in the ovary following BNF administration. CYP1A1 mRNA was increased in the ovary and kidney, suggesting the presence of AHR in rainbow trout ovary, while the AHR agonist produced no effect on Nramp mRNAs.

Demonstration of 2,3,7,8-tetrachlorodibenzo-p-dioxin attenuation of P450 steroidogenic enzyme mRNAs in rat granulosa cell in vitro by competitive reverse transcriptase-polymerase chain reaction assay

We investigated the effects of 2,3,7,8-tetrachlorodibenzo-p-dioxin (TCDD), in prepubertal (PP) and adult (A) rat granulosa cells (GC) in vitro by examining the changes in estrogen secretion, aromatase enzyme activity and mRNAs for steroidogenic enzymes P450scc, 3beta-HSDI, P450arom; and for components of the AHR signaling pathway-CYP1A1, aromatic hydrocarbon receptor (AHR), and the AHR nuclear translocator protein (ARNT). In PP and A rat GC, TCDD (3.1 nM) reduced estrogen secretion at 48 h without altering aromatase enzyme activity. Addition of FSH (50 ng/ml) increased aromatase activity in GC with or without TCDD. FSH-induced aromatase activity was significantly reduced by TCDD (3.1 nM) at 48 h. Semi-quantitative RT-PCR showed a significant increase in CYP1A1 mRNA both at 24 and 48 h with TCAP, while a significant reduction in P450scc and P450arom mRNA was observed with competitive RT-PCR. All steroidogenic enzyme mRNAs were significantly lower in adults than in PP GC. We conclude that in rat GC, TCDD modulates the level of cytochrome P450 enzymes involved in the steroid biosynthetic cascade. This effect may be attributable to AHR interaction with dioxin-responsive elements present in the genes encoding these enzymes.

Minimal endocrine alterations in rodents after consumption of lake trout (Salvelinus namaycush)

Polychlorinated biphenyls (PCBs) and dioxins are known to cause disruptions in circulating hormone concentrations, which may influence fertility and normal fetal development. Structure activity relationships have been determined for individual congeners, but it is unclear what impacts occur due to exposure to complex mixtures of chemicals found in the environment. Most laboratory studies of PCB exposure have used commercial mixtures in high doses, which may not be representative of environmental concentrations of individual congeners, nor accurately represent complex interactions of multiple contaminants. The present study investigated endocrine alterations in rats associated with the consumption of lake trout collected from three specific locations in the Great Lakes. Composite fish samples were analyzed for PCBs, organochlorines, and mercury and ranged from 415 ppb to 1,275 ppb for individual contaminants. Fillet composites were fed to timed-pregnant Long-Evans rats as 30% of their diet. Concentrations of total thyroxine and estrogen were not significantly different in offspring of dosed dams from that of controls. However, aromatase activity was lowered in all dosed groups as compared with controls. This may represent a lowered expression of the CYP 19 gene in exposed rats or may be due to the presence of one or more substances in the contaminants that are capable of altering the affinity of the aromatase enzyme for its normal endogenous substrate. It is also possible that the number of maturing follicles in the lake trout-fed rats may be fewer than controls, which would result in an overall reduction in the enzyme activity. Data regarding the endocrine effects of environmental contaminant mixtures found in fish from the Great Lakes Basin are still controversial. Additionally, information is scarce with respect to the F1 generation of laboratory animals following environmental maternal exposures, therefore, we investigated the reproductive-endocrine alterations in rat offspring associated with the consumption of lake trout (Salvelinus namaycush) collected from three areas in the Great Lakes.

Estrous cycle-dependent changes in the expression of aromatic hydrocarbon receptor (AHR) and AHR-nuclear translocator (ARNT) mRNAs in the rat ovary and liver

The aromatic hydrocarbon receptor (AHR) and AHR nuclear translocator protein (ARNT) mediate the toxic effects of a wide variety of halogenated and polycyclic aromatic hydrocarbons. While it can be assumed that AHR has an endogenous function, its role in reproduction is currently undefined. The present study seeks to examine the regulation of AHR and ARNT mRNAs in liver and ovarian tissues across the rat estrous cycle. Message for hepatic AHR was increased significantly on the morning of proestrus, and decreased dramatically by the evening of proestrus; while hepatic ARNT mRNA was significantly decreased between diestrus and the morning of proestrus, and between the evening of proestrus and the morning of estrus. Ovarian AHR mRNA was unchanged from diestrus to proestrus, and was decreased on the evening of proestrus. Changes in the expression of ARNT mRNA mirrored changes in the liver. To assess interaction between the AHR- and estrogen-receptor (ER)-signaling pathways and to test the hypothesis that estrogen regulates AHR mRNA, 25-day-old female rats were injected with either 17beta-estradiol, the ER antagonist ICI 182 780, or with vehicle, and hepatic AHR mRNA was measured. Treatment with estrogen or the estrogen antagonist did not alter the abundance of AHR mRNA in the liver. These data suggest that while estrogen may not be the key regulator of AHR mRNA expression, a factor associated with the rat reproductive cycle may be important in regulating the expression of both the AHR and ARNT genes in the ovary and liver.

Secretion of ovarian inhibin and its physiologic roles in the regulation of follicle-stimulating hormone secretion during the estrous cycle of the female guinea pig

To characterize inhibin secretion during the estrous cycle in guinea pigs, the concentrations of plasma inhibin, estradiol, progesterone, and FSH were determined. A significant positive correlation was observed between inhibin and estradiol throughout the estrous cycle. Plasma inhibin and estradiol started to increase a few days before ovulation (Day 0 = day of estimated ovulation), and decreased after ovulation. These two hormones remained low during the luteal phase. The immunoreactivity of inhibin alpha, betaA, and betaB subunits was colocalized in the granulosa cells of one or two healthy large follicles in the ovary before ovulation. There was no positive reaction of inhibin alpha and beta subunits in the corpora lutea or other follicles. Ovariectomy resulted in an abrupt decrease in plasma inhibin and a significant increase in plasma FSH. Injection of anti-inhibin serum into adult female guinea pigs induced an elevation in plasma FSH in a dose-dependent manner. This report presents the first description of sequential changes in plasma inhibin and estradiol during the estrous cycle of guinea pigs. Results suggest that inhibin is secreted mainly by granulosa cells of a few healthy large follicles in the ovary and that it plays an important role in the regulation of FSH secretion during the estrous cycle in guinea pigs.

Dioxin perturbs, in a dose- and time-dependent fashion, steroid secretion, and induces apoptosis of human luteinized granulosa cells

Dioxin (2,3,7,8-tetrachlorodibenzo-p-dioxin; TCDD) is the most toxic congener of a large class of environmental pollutants. Several studies have shown that TCDD exposure reduced fecundity and ovulatory rate in rats and increased the incidence of endometriosis in monkeys. Recent work suggests that TCDD's endocrine-disrupting effects are, at least in part, caused by a direct action at the ovary. Although the factors involved in TCDD-induced toxicity are still under investigation, several studies have shown that TCDD induces programmed cell death, or apoptosis, in various tissues and may act in a similar fashion in the ovary. In the present study, we set out to evaluate the in vitro effects of TCDD on steroid secretion, specifically estradiol-17beta (E2) and progesterone, by human luteinized granulosa cells (LGC), and to further determine whether TCDD is capable of inducing apoptosis in this cell type. Human LGC were obtained from women participating in an in vitro fertilization program. Medium, with or without three different concentrations of TCDD and substrates [androstenedione (A4) or pregnenolone], was added to each culture. The media were collected at 4, 8, 12, 24, 36, and 48 h and were assayed by RIA. At 24 and 48 h, the LGC were fixed for assessment of DNA fragmentation via an in situ immunofluorescence technique. Transmission electron microscopy was also performed on LGC after 24 and 48 h with TCDD. TCDD, at all concentrations tested (3.1 pM, 3.1 nM, and 3.1 microM), significantly reduced E2 accumulation in the media at 8, 12, and 24 h, compared with controls. At 36 and 48 h, TCDD treatment (at 3.1 microM) caused a significant increase in E2, compared with controls. The effect of TCDD on E2 was abolished with the addition of A4. TCDD treatment did not alter progesterone accumulation. Apoptosis increased at 24 h with 3.1 microM TCDD, with no apparent effect at 3.1 nM. By 48 h, however, TCDD increased apoptosis in a dose-dependent manner. Transmission electron microscopy showed ultrastructural differences in LGC with 3.1 microM TCDD at 24 and 48 h. Collectively, the results of the present study suggest that TCDD perturbs E2 secretion by depletion of A4 precursor and increases apoptotic cell death of human LGC in a dose- and time-dependent fashion.

Reduced fertility in female mice lacking copper-zinc superoxide dismutase

Copper-zinc superoxide dismutase (CuZn-SOD) is believed to play a major role in the first line of antioxidant defense by catalyzing the dismutation of superoxide anion radicals to form hydrogen peroxide and molecular oxygen. Recent studies have shown that missense mutations in this gene contribute, evidently through a gain-of-function mechanism, to about 20% of familial amyotrophic lateral sclerosis. To define further the physiologic role of this enzyme, a model of mice deficient in this enzyme was generated using gene targeting technology. Mice lacking this enzyme were apparently healthy and displayed no increased sensitivity to hyperoxia. However, they exhibited a pronounced susceptibility to paraquat toxicity. Most surprisingly, female homozygous knock-out mice showed a markedly reduced fertility compared with that of wild-type and heterozygous knock-out mice. Further studies revealed that although these mice ovulated and conceived normally, they exhibited a marked increase in embryonic lethality. These data, for the first time, suggest a role of oxygen free radicals in causing abnormality of female reproduction in mammals.

Modulation of ovarian follicle maturation and effects on apoptotic cell death in Holtzman rats exposed to 2,3,7,8-tetrachlorodibenzo-p-dioxin (TCDD) in utero and lactationally

Recent reports have described the reproduction-modulating and endocrine-disrupting effects following exposure to toxic substances such as 2,3,7,8-tetrachlorodibenzo-p-dioxin (TCDD). Herein, we set out (1) to determine whether TCDD exposure exerts detrimental effects on follicle maturation in the Holtzman rat ovary and (2) to determine whether the effects of TCDD are mediated in part via apoptotic cell death. In certain species, dioxin exposure is correlated with reduced fecundity, reduced ovulatory rate, an increased incidence of endometriosis, and various reproductive cancers. Although some of the effects of TCDD are mediated via the hypothalamic-pituitary axis, direct effects on the ovary have also been observed. In the present study, an oral dose of 1 microgram TCDD/kg maternal body weight was administered on Day 15 of gestation. Female pups were sacrificed on Postnatal Day 21/22, and the ovaries were excised, fixed for histologic analysis, and analyzed in a double-blind paradigm. The analysis included a count and measurement and classification of preantral and antral follicles throughout the entire ovary. The contralateral ovary from each animal was analyzed for DNA fragmentation indicative of apoptotic cell death. The results indicate that TCDD treatment significantly reduced the number of antral follicles in the size classes 50,000 to 74,999 microns2 and > 100,000 microns2. We also observed a reduction in the number of preantral follicles less than 50,000 microns2. No difference was observed in the degree of apoptotic cell death in antral (50,000 to > 100,000 microns2) and preantral follicles (50,000 microns2 to > 75,000 microns2) between TCDD-treated and control-treated tissues. These data support the hypothesis that TCDD results in a diminution in the number of antral and preantral follicles of certain size classes in animals exposed during critical periods of development, but that apoptosis does not appear to be the underlying mechanism in these particular follicles. This does not preclude apoptosis occurring in pools of smaller precursor follicles.

Alterations to the pituitary-gonadal axis in the peripubertal female rat exposed in utero and through lactation to 2,3,7,8-tetrachlorodibenzo-p-dioxin

The environmental pollutant 2,3,7,8-tetrachlorodibenzo-p-dioxin (TCDD; dioxin) is a potent disrupter of vertebrate endocrine systems. It was shown previously that in utero and lactational (IUL) exposure to TCDD resulted in a reduction in serum estradiol concentrations; however, the mechanism for this remains unknown. In the current study, the effects of perinatal exposure to TCDD on the pituitary-ovarian axis were examined. Pregnant rats were given a single oral dose of 1 microg TCDD/kg or vehicle as control on gestation Day 15, and female pups were killed on postnatal Day 21. Pituitaries were assayed for gonadotropin beta-subunit mRNA; additional pituitaries were cultured for 4 h and the media were assayed for FSH. Gonadotropin receptor mRNAs from vehicle- and TCDD-exposed animals were compared, with some ovaries cultured and the media assayed for estrogen secretion. LH, FSH, progesterone, and androstenedione concentrations were determined in serum. IUL exposure to TCDD resulted in a significant reduction of pituitary FSHbeta mRNA. Although estrogen output was shown to be reduced, neither serum FSH nor LH concentration was increased significantly, and FSH secretion in vitro was not altered. Similarly, serum progesterone and androstenedione were not altered by TCDD exposure, while in vitro estrogen secretion was significantly reduced. These data suggest that TCDD did not act on serum gonadotropin concentrations. The reduction in the concentration of serum estrogen appears to result from direct or indirect actions on the ovary at some point following androstenedione production.

Estrogen receptor and aromatic hydrocarbon receptor in the primate ovary

We have previously shown by immunocytochemistry and autoradiography the presence of estrogen receptors (ER) in rhesus monkey ovary. Intense chromogen staining showed specific binding for ER in nuclei of germinal epithelium and granulosa cells of antral follicles; and radiolabeled ligand bound specifically to functional corpora lutea (CL). Although it is accepted that the germinal epithelium of the primate ovary contains ER, some controversy still persists regarding the intraovarian localization of this molecule. In addition, no data exist that localize the aromatic hydrocarbon (dioxin) receptor (AHR), which is known to modulate ER, to the primate ovary. In the present study, we show the presence of ER using Western blot analysis, and ER capable of binding DNA within intraovarian compartments in two species of the genusMacaca (rhesus macaque,Macaca mulatta and stumptail macaque,Macaca arctoides); extend these findings to human ovarian granulosa cells (GC) using Western blot, reverse transcription-polymerase chain reaction (RT-PCR), and gel mobility-shift analysis; and localize the AHR to intraovarian compartments of the macaque ovary by Western blots and gel-shift assays. These experiments strongly suggest that estrogens can exert effects on follicle development directly at the ovary, and provide the first direct evidence that AHR-mediated toxicity may be manifested at the ovary to induce possible antifertility effects.

Modulation of growth axis gene expression by in utero and lactational exposure to 2,3,7,8-tetrachlorodibenzo-p-dioxin (TCDD) in the weaning Holtzman rat

While thein utero and lactational effects of 2,3,7,8-tetrachlorodibenzo-p-dioxin (TCDD) on both male and female reproductive systems appear to be severe, little is known about its effects on the developing growth axis. The objective of this study was to describe changes in growth axis gene expression that accompany exposure to TCDD duringin utero and lactational development. Pregnant Holtzman rats were administered 1 μg TCDD/kg maternal body weight or vehicle control on gestational day 15 by gavage. Using ribonuclease protection assays, we compared mRNA levels measured in 21-d-old female pups exposed to TCDD with levels measured in control animals for the following genes: somatostatin, growth hormone-releasing hormone (GHRH), hypothalamic and pituitary galanin (GAL), growth hormone (GH), and insulin-like growth factor-I (IGF-I). Serum GH concentrations measured by radio-immunoassay were significantly increased, although GH mRNA levels were unchanged from controls by TCDD exposure. Hypothalamic GAL mRNA was decreased in TCDD-treated animals, whereas pituitary GAL mRNA in TCDD-treated animals was not altered. GHRH mRNA was increased in hypothalami from TCDD-exposed animals. IGF-I mRNA in the liver was decreased to 67% of controls. These data indicate that the growth axis is sensitive to the effects of TCDD delivered during critical periods of development. The alterations observed in growth axis gene expression with exposure to TCDD add to the body of data demonstrating a potent effect of this compound on the fetal and neonatal endocrine system.

In utero and lactational exposure of female Holtzman rats to 2,3,7,8-tetrachlorodibenzo-p-dioxin: modulation of the estrogen signal

The environmental pollutant 2,3,7,8-tetrachlorodibenzo-p-dioxin (TCDD; dioxin) induces severe reproductive defects in male rats when exposure occurs in utero and during lactation. Yet there is currently a paucity of information regarding the effects of this exposure paradigm in females. In the current study, we examine the effects of TCDD during fetal and perinatal development on the estrogen-signaling system in peripubertal female rats. Pregnant Holtzman rats were given 1 microgram/kg TCDD or vehicle control by gavage on gestational Day 15. Body weights were reduced, though not significantly, on postnatal Day 21. While ovarian and uterine wet weights were not increased by TCDD exposure, the percentage of body weight attributed to the ovary was increased significantly. Through use of ribonuclease protection and gel-shift assays, exposed females were compared with nonexposed counterparts for estrogen receptor (ER) mRNA and DNA-binding activity in the following tissues: hypothalamus, pituitary (mRNA only), uterus, and ovary. ER mRNA levels increased in the hypothalamus, uterus, and ovary, and decreased in the pituitary. The results of the DNA-binding assays paralleled the mRNA results in the uterus, while DNA-binding activity was decreased in the hypothalamus and was unchanged in ovarian protein extracts. Circulating concentrations of estrogen were significantly lower in TCDD-exposed rats than in controls. These data suggest that the decrease in serum estrogen may be a cause of the alterations in ER mRNA; the changes in ER DNA-binding activity may indicate alterations in either translation or posttranslational receptor processing. Overall, this study shows that TCDD may act systemically in this model, and these effects should not necessarily be characterized as antiestrogenic.

Effects of follicle-stimulating hormone administration on oestradiol-induced cystic ovaries in guinea pigs

A consistent defect in follicle-stimulating hormone (FSH) secretion is seen in humans with Polycystic Ovarian Syndrome (PCOS); therefore, we evaluated whether Metrodin (a highly purified urinary FSH) administration concurrent with cyst induction or following cyst induction inhibits estrogen-induced cyst development and augments ovarian follicular growth in an established guinea pig model. All animals in these studies received subcutaneous implants containing oestradiol-17 beta (E2)-filled Silastic capsules for a 48-hour period. Guinea pigs in study #1 were administered four 0.25 mL injections of FSH or placebo at twelve-hour intervals simultaneously with the E2 treatment; guinea pigs assigned to study #2 were administered four 0.25 mL injections of FSH or placebo at twelve-hour intervals following the induction of the cystic condition by E2. Exogenous FSH appears to negate cyst formation when superimposed upon the cyst-inducing agent (E2). Further, treatment with FSH augmented the number of mid-sized follicles in both paradigms. This study is the first to establish evidence of an anti-cystic effect of FSH in an animal model.

Neurotrophin-3 augments steroid secretion by hamster ovarian follicles in vitro

Innervation of the ovary is known to be affected by neurotrophic factors; mRNA for some of these molecules and their low-affinity receptors have been identified in ovarian follicular tissue. We attempted to determine whether neurotrophin (NT-3) exerts a non-neuronal impact on the ovary, affecting follicular estradiol secretion via a possible humoral action. Ovaries were excised from mature Golden Syrian Hamsters (Mesocricetus auratus) and large preovulatory follicles were removed by microdissection. Follicles were incubated for 72 hr in control medium, or medium containing 10 ng, 100 ng, or 1000 ng/ml NT-3. After culture, medium samples were assayed for estradiol content. NT-3 exerted dichotomous effects, depending on concentration: NT-3 augmented mean estradiol output two-fold at 100 ng/ml, while 1000 ng/ml NT-3 decreased estradiol secretion back to control levels. By 48-72 hr in culture, all groups exhibited a significant decline in mean estradiol secretion due presumably to diminished viability, independent of neurotrophin action. These data suggest a humoral role for NT-3 in estradiol secretion of preovulatory follicles in culture.

Elevated follicular fluid angiotensin II and pregnancy outcome

OBJECTIVE

To assess whether a relationship exists between follicular fluid (FF) angiotensin II (AII) concentration and pregnancy outcome or earlier fecundity parameters and whether correlations exist among FF AII concentrations and P, E2, T, androstenedione (A), or various ratios of these.

DESIGN

Retrospective study in which hormone concentrations in FF samples were measured.

SETTING

In vitro fertilization clinic-Assisted Reproductive Technology Program, Rush Medical Center.

PATIENTS

Twenty-six female patients underwent ovarian stimulation for IVF.

INTERVENTION

Leuprolide acetate was combined with hMG and FSH for ovarian stimulation.

MAIN OUTCOME MEASURE

Follicular fluid aspirates were collected and oocytes were recovered 34 to 36 hours after hCG injection. The patients proceeded to undergo IVF and ET. Follicular fluid hormones were measured using standard RIA. Angiotensin II and steroid hormone concentrations in FF were compared for pregnant versus nonpregnant women using the Student's t-test and rank-sum test. Pearson multiple-correlation analysis was performed to calculate correlation coefficients among AII concentrations and steroid concentrations in FF aspirates.

RESULTS

Mean FF concentration of AII was significantly lower in samples from women showing clinical pregnancies (112.2 +/- 13.9 pg/mL [107.3 +/- 13.3 pmol/L]) compared with samples from women who did not achieve pregnancy (217.1 +/- 23.8 pg/mL [207.5 +/- 22.7 pmol/L]) (mean +/- SE). A negative correlation was observed between FF concentrations of AII and P. Correlations of AII with E2, T, A, or with ratios of these did not show significance.

CONCLUSION

These data suggest that high AII concentration at time of oocyte recovery may indicate poor pregnancy outcome in women undergoing ovarian stimulation for IVF. These data corroborate previous results in animal models showing that AII predisposes follicles to undergo atresia-like conditions.

Role and site of estrogen action in follicular atresia

Subsequent to an initial understanding that estrogen was only stimulatory to folliculogenesis, we have come full circle to the present recognition that many actions of estrogen are inhibitory to follicular function. The development of this interpretation has frequently been associated with the controversial issue o f the likely site o f estrogen action, especially in primates, where much of the evidence has been amassed. The accumulated findings in a variety of species seem to demonstrate clearly that at least part of the atretogenic effect of estrogen is exerted directly on the ovary, apparently by interaction with the nuclear estrogen receptor. Recent observations include identification of messenger RNAs for the estrogen receptor and for creatine kinase in the macaque ovary, and a current focus is to localize messages within specific compartments of the ovary.

Induction by estradiol-17 beta of polycystic ovaries in the guinea pig

In the present study we wished to develop a model for polycystic ovarian syndrome (PCOS) using the guinea pig, because this animal's cycle, compared to other rodent models, more closely emulates that of humans. Four silastic capsules, either empty or containing cholesterol or estradiol-17 beta, were placed subcutaneously for 48 h on Day 10 or 12 of the cycle. Vaginal smears were taken daily. Cardiac blood was drawn at various intervals. At necropsy, trunk blood was collected and ovaries were excised and analyzed histologically. Cycle length was extended over that in controls in animals treated with estradiol-17 beta (E2) on Day 12 of the cycle. Treatment with E2 resulted in an increase in serum estrogen 2 h after capsule insertion. No changes were evident in progesterone or androstenedione concentrations with treatment. Animals treated with E2 and killed late (54 days after capsule removal) showed cysts grossly (group A), while occult cysts were present in E2-treated animals killed early (17 days; group B); no cysts were observed in control groups. Ovarian weight and size were increased in group A over controls. There was an increase in the fraction of atretic:total follicles < 500 mm in size in group A compared to group B as well as compared to controls. Since these results are similar to those seen in human PCOS, we conclude that the guinea pig may serve as an exceptional and unique model for the study of PCOS and may be applicable to humans.

In-vitro effects of angiotensin II on steroid production by hamster ovarian follicles and on ultrastructure of the theca interna

Angiotensin II (AII) is present in the mammalian ovary and has been correlated with atresia in follicles. Since the theca interna may be one site at which atresia is initiated, we wished to determine whether AII exerts an effect on theca interna from explanted ovarian follicles of hamsters. Hamsters were sacrified on the morning of proestrus, and ovaries were removed. Preovulatory follicles were excised from the ovaries, and cultured with one of the following components: medium alone (control); medium plus AII (1 x 10(-6) M); the AII-receptor antagonist [Sar1, Ile8] AII (1 x 10(-4) M); or AII plus antagonist. After 72 h, the follicles were processed for transmission electron microscopy (to determine quantities of theca interna organelles involved in the steroid synthetic pathway) or for protein determination (to normalize steroid production rates). The incubation medium was drawn off and analyzed by radioimmunoassay for progesterone, androstenedione, or estradiol-17 beta. There was a significant positive correlation (r = 0.92, P less than 0.01) between follicular androstenedione secretion and area comprising theca interna smooth endoplasmic reticulum. In the theca interna, AII induced a two-fold and 1.6-fold increase in lipid droplet number and area comprising smooth endoplasmic reticulum, respectively (P less than 0.05). Excess antagonist negated the increase in cell organelles and also reduced androstenedione secretion compared with AII alone (P less than 0.05). Most importantly, AII significantly augmented the ratio of androstenedione:estradiol-17 beta secretion by 44% over that of control. The ultrastructural changes observed in this study and the increase in the androstenedione:estradiol-17 beta production ratio are consistent with atresia-like changes in ovarian follicles.(ABSTRACT TRUNCATED AT 250 WORDS)

Effects of equine chorionic gonadotropin on reproductive performance in anestrous mink

The incidence of anestrous mink during the normal breeding season has been reported to be as high as 5%. We sought to induce estrus in these mink by using various doses of equine chorionic gonadotropin (eCG) and human chorionic gonadotropin (hCG). Seventy-five female mink maintained under standard ranch conditions failed to demonstrate estrus during the annual breeding season in March. These anestrous mink were randomly assigned to treatment groups. Treatments were given on March 16 and again on March 18. On these 2 d, mink were treated with equal doses of saline, 25, 50, or 100 IU of eCG, or 50 IU of eCG on March 16 and 50 of IU of eCG + 100 IU of hCG on March 18. Females were paired with males beginning on March 22. None of the saline-treated mink mated. In contrast, reproductive performance of the anestrous mink was significantly improved by treatment with eCG. This included proportion of mink breeding (47 to 100%), proportion giving birth (33 to 80%), and average litter size (2.6 to 4.0 kits per whelping female). Reproductive efficiency improved with increasing doses of eCG and was not further improved by addition of hCG. These results demonstrate that eCG has a potential application for treating anestrous mink during the breeding season.