Ovarian Progesterone Production Research Articles

Assessment of steroid disruption using cultures of whole ovary and/or placenta in rat and in human placental tissue.

The paper presents results of collaborative research on cadmium as an endocrine disruptor. To detect steroidogenic alterations in cycling and pregnant rats following cadmium exposures in vivo (at 3 or 5 mg/kg as a single s.c. dose) and in vitro (from 0 through 2000 microM Cd(2+)) whole-ovary culture was used. To evaluate steroid productions in rats fed low iron (10 ppm) and concomitantly exposed to cadmium (5 mg/kg total dose by s.c.-implanted osmotic pumps) during 19 days of pregnancy whole-placenta culture was also used. In human placental tissue cadmium and progesterone concentrations were assessed in relation to cigarette smoking. Cultures of minced ovaries were evaluated for 1-h basal steroid production and following 1-h production stimulated with either human chorionic gonadotropin (hCG) or hCG and pregnenolone. Placental cultures were evaluated for average 1-h progesterone production following 3 h of unstimulated production. Steroid hormones were evaluated by specific radioimmunoassay. Placental cadmium concentrations were analyzed by atomic absorption spectrometry. In-vivo cadmium exposure interfered with normal steroidogenesis in cycling rats and in early pregnancy, with ovarian estradiol production the most affected. Under in-vitro cadmium exposure the most affected was ovarian production of progesterone and testosterone in cycling (proestrous) rats with medial inhibitory concentrations under 500 micro M Cd(2+). Cadmium interfered with the steroidogenic pathway at more than one site. Linear and additive effects of low-iron feeding and concomitant cadmium exposure during pregnancy on placental progesterone production were found. In humans, we found that the placentas of smoking mothers contained twice as much cadmium and approximately half the amount of progesterone than did the placentas of non-smoking mothers. Results of the research on cadmium-induced steroidogenic effects using cultures of whole rat ovary and/or placenta as well as human placental tissues point to cadmium as an endocrine disruptor that may compromise pregnancy outcome and fetal viability.

Hepatic lipase deficiency attenuates mouse ovarian progesterone production leading to decreased ovulation and reduced litter size.

The lipolytic enzyme hepatic lipase (HL) may facilitate mobilization of cholesterol substrate for ovarian steroidogenesis. We investigated whether HL was necessary for optimum reproduction in the female mouse by analyzing breeding performance and ovarian responses to gonadotropins in HL-/- mice. HL-/- female mice bred with HL-/- males had the same pregnancy success rate and pup survival rate as did wild-type (WT) mice but had significantly smaller litters, producing 1.7 fewer pups per litter. Mice were primed with eCG/hCG, and at 6 h post-hCG the HL-/- mice had smaller ovaries than did the WT mice. HL deficiency specifically affected ovarian weight; adrenal gland weights did not differ between WT and HL-/- mice. HL-/- mice weighed more than age-matched WT mice. Between the two mouse genotypes, uterine weights were the same, indicating that estrogen production was equivalent. However, the HL-/- ovaries produced significantly less progesterone than did the WT ovaries within 6 h of hCG stimulation. HL-/- ovaries had the same number of large antral follicles as did the WT ovaries but had fewer hemorrhagic sites, which represent ovulations, fewer corpora lutea, and more oocytes trapped in corpora lutea. We suggest that reduced progesterone synthesis following hCG stimulation attenuated the final maturation of preovulatory follicles, resulting in smaller ovaries. Furthermore, reduced progesterone production limited the expression of proteolytic enzymes needed for tissue remodeling, resulting in fewer ovulations with a corresponding increase in trapped or unovulated oocytes and providing a possible explanation for the smaller litter size observed in spontaneously ovulating HL-/- mice.

Suppression of ovarian progesterone production in dairy cows using an implant of GnRH‐agonist (deslorelin) for the purpose of evaluating

Suppression of ovarian progesterone production in dairy cows using an implant of GnRH‐agonist (deslorelin) for the purpose of evaluating

Ovarian steroid hormone production in a multiple ovulating male line and a single ovulating traditional line of turkeys

Ovarian production of oestradiol and progesterone was investigated in a single ovulating traditional line and a multiple ovulating male line of turkeys. The oestradiol output from small follicles in response to LH stimulation and the aromatase activity of the residual ovary were also compared. The multiple hierarchy of follicles in the male line was shown to consist of a series of follicles of a similar size and stage of physiological maturation. The follicles of the traditional line produced significantly greater quantities of oestradiol than those of the male line. Impaired oestradiol production may have resulted in the lower plasma oestradiol concentration observed in the male line. There was no difference in follicular progesterone output between the traditional-line and male-line turkeys. The oestradiol output of whole small white follicles in response to LH stimulation was similar in the two lines and the depressed steroidogenesis of the male line was not changed. The aromatase activity of the small follicles was also lower in the male line, and there was no evidence that the male line ovary produced oestradiol in quantities proportional to its size. The results demonstrated that the hierarchy of follicles in the male line consisted of groups of follicles of similar mass and hormone output and indicated that selection for increased meat yield may have resulted in reduced ovarian steroidogenesis in male-line turkeys, in comparison with traditional, unselected turkeys.

Ovarian steroid hormone production in a multiple ovulating male line and a single ovulating traditional line of turkeys

Ovarian production of oestradiol and progesterone was investigated in a single ovulating traditional line and a multiple ovulating male line of turkeys. The oestradiol output from small follicles in response to LH stimulation and the aromatase activity of the residual ovary were also compared. The multiple hierarchy of follicles in the male line was shown to consist of a series of follicles of a similar size and stage of physiological maturation. The follicles of the traditional line produced significantly greater quantities of oestradiol than those of the male line. Impaired oestradiol production may have resulted in the lower plasma oestradiol concentration observed in the male line. There was no difference in follicular progesterone output between the traditional-line and male-line turkeys. The oestradiol output of whole small white follicles in response to LH stimulation was similar in the two lines and the depressed steroidogenesis of the male line was not changed. The aromatase activity of the small follicles was also lower in the male line, and there was no evidence that the male line ovary produced oestradiol in quantities proportional to its size. The results demonstrated that the hierarchy of follicles in the male line consisted of groups of follicles of similar mass and hormone output and indicated that selection for increased meat yield may have resulted in reduced ovarian steroidogenesis in male-line turkeys, in comparison with traditional, unselected turkeys.

Ovarian steroidogenic responsiveness to exogenous gonadotropin stimulation in young and middle-aged female rats.

Reproductive aging in the female rat is associated with gradual declines in LH secretion and ovarian progesterone (P) production. This study examined whether the influences of aging on P levels reflect decreased ovarian responsiveness to gonadotropin stimulation, as opposed to changes in gonadotropin release. Young and middle-aged regularly cyclic female rats received sodium pentobarbital to block endogenous proestrous luteinizing hormone (LH) surges, followed by administration of various doses of human chorionic gonadotropin (hCG). Similar treatments were performed in middle-aged acyclic persistent-estrous (PE) females. Injection of hCG resulted in equivalent plasma hCG levels in each treatment group. At the lowest hCG dose tested, a significant rise in plasma P levels was observed in middle-aged cyclic rats, but not in young cyclic or middle-aged PE females. This unexpected finding may reflect accelerated follicular development in middle-aged cyclic females, as suggested by a previous study. At the intermediate dose, young and middle-aged cyclic but not PE rats displayed significantly increased P in response to hCG. At the highest dose tested, all three groups of rats displayed increased P levels after hCG stimulation. However, P concentrations were significantly lower in middle-aged PE than regularly cyclic females. Northern and slot blot hybridization analyses revealed that ovarian mRNA levels for cytochrome P450 side-chain cleavage, the rate-limiting enzyme in P synthesis, were markedly reduced in PE rats following hCG stimulation. These findings indicate that ovarian responsiveness to gonadotropin stimulation is impaired in middle-aged PE, but not regularly cyclic rats, and suggest influences of cycle status on the biochemical and molecular mechanisms regulating ovarian steroid production. Furthermore, these findings reveal that attenuated P production in middle-aged proestrous rats is due to attenuated preovulatory LH surges, rather than decreased ovarian sensitivity to LH.

What causes low rates of child-bearing in congenital adrenal hyperplasia?

Women with classical congenital adrenal hyperplasia (CAH) have relatively low fertility rates (1–4). The largest clinic population was studied by Mulaikal et al. (2) who conducted a questionnaire survey of the Johns Hopkins Hospital sample of women with classical 21-hydroxylase deficiency and obtained responses from 80 of them (71% of the eligible women; age range, 18–69 yr; mean, 33 yr), evenly split into the simple virilizing (SV) and salt-wasting (SW) forms. Half of the women were not heterosexually active. Those who were heterosexually active nevertheless appeared to have low fertility. Among the 25 SV women who reported both adequate vaginal reconstruction and heterosexual activity, the fertility rate was 60%. Only 15 became pregnant, and 13 of these gave birth (9 by cesarian section because of cephalopelvic disproportion); the other 2 had an abortion, 1 spontaneous and the other induced. Among the 15 SW women with both adequate introitus and heterosexual activity, the fertility rate was 7%. Only 1 reported a pregnancy, and that ended in an elective termination. Mulaikal et al. suggested three mechanisms underlying the low fertility in CAH women overall: 1) insufficient hormonal control of the hyperandrogenemia by glucocorticoid replacement therapy (and possibly long term effects of prenatal and postnatal androgen excess), 2) insufficient vaginal reconstruction resulting in inability to engage in coitus, and 3) absence of heterosexual activity, which in some women was associated with homosexuality. In an accompanying editorial, Federman (5) suggested potential additional factors that might contribute to the low fertility in CAH: an impaired reproductive self-image related to vaginal inadequacy and “a male psychosexuality” as a consequence of putative masculinization of the fetal brain. The purpose of the present paper is to revisit the issue, review the status of the empirical evidence, especially the role of behavioral determinants, and suggest additional hormone-related psychological factors that may contribute to the low fertility rates of CAH women. The most widely recognized cause of the low rate of fertility among CAH women remains nonoptimal hormonal control. Ovulatory failure secondary to steroid excess is an important barrier to conception in many CAH women. There is considerable evidence suggesting that the steroid excess is not just an outcome of ACTH oversecretion (6). Among the other contributing factors appear to be 1) a mild degree of ACTH hyperresponsiveness to CRH; 2) altered enzyme kinetics, namely reduced catalytic efficiency of the mutated 21-hydroxylase with resulting increases in the precursor hormones progesterone and 17-hydroxyprogesterone even in the presence of excess glucocorticoid administration; 3) overactivation of the renin-angiotensin-aldosterone axis with ensuing stimulation of adrenocortical biosynthesis; and 4) alterations of the hypothalamic-pituitary-ovarian axis as indicated by abnormal gonadotropin dynamics, polycystic ovaries, and excess ovarian production of progesterone, 17hydroxyprogesterone, and androgens (6). Consequently, new combination treatments that go beyond mere ACTH suppression are being developed to improve the overall quality of hormonal control in CAH (7). Much evidence has accumulated that implicates psychological factors in the overall reduction of fertility in women with classical CAH. Reduced heterosexual activity compared to controls has been documented in a number of studies. During adolescence, women with classical CAH as a group tend to have delayed (or absent) heterosexual milestones, such as dating, sexual initiation, and falling in love (3, 8–13). In adulthood, fewer are heterosexually active, in steady relationships, or married (2, 9–13). For all of these behaviors, it is predominantly women with the SW variant who differ from controls, much more so than those with the SV variant (4, 9, 11). Not only overt sexual activity with a partner is delayed or reduced. The frequency of sexual imagery, such as romantic/ erotic fantasies and dreams, the intensity of experienced sexual motivation (drive, libido), and the capacity to fall in love also seem to be markedly lower in CAH women as a group, especially those with the SW condition, than in controls (9, 10, 12, 13), although a few CAH women complain of excessive libido, especially when untreated or when treatment lapses. The reduction of heterosexual activity is likely to stem from several causes. One is an increased rate of bior homosexuality in women with classical CAH, as demonstrated especially in sexual imagery such as erotic/romantic fantaReceived January 11, 1999. Accepted February 24, 1999. Address all correspondence and requests for reprints to: Dr. H. F. L. Meyer-Bahlburg, New York State Psychiatric Institute, Unit 15, New York, New York 10032-2695. 0021-972X/99/$03.00/0 Vol. 84, No. 6 The Journal of Clinical Endocrinology & Metabolism Printed in U.S.A. Copyright © 1999 by The Endocrine Society

Coming to term with GABA

Oxytocin, the most powerful uterotonic agent known, is released from the pituitary gland in large amounts during parturition in all placental mammals studied so far, including humans. Although parturition can proceed in its absence, oxytocin is thought to play an important role (see Russell & Leng, 1998). In the rat, pregnancy normally lasts for 21 days. About 24 h before the pups are born, increased production of prostaglandins by the uterus induces luteolysis, and ovarian progesterone production falls dramatically. This fall is an essential prelude to parturition; if prevented, then the rat pups will remain unborn. The fall leads to a further increase in prostaglandin production, and, directly or indirectly, to a host of changes that prepare the uterus and birth canal for parturition. In the last few hours of pregnancy, oxytocin receptors appear in high concentrations in the uterus, and establish a positive-feedback loop between the uterus and the hypothalamic oxytocin system. Uterine contractions, triggered by prostaglandins, excite the oxytocin cells, and oxytocin release triggers further prostaglandin production and further uterine contraction. Thus progesterone plays a critical role in the timing of parturition through its peripheral actions (see Leng & Brown, 1997). A paper in this issue of The Journal of Physiology (Brussaard et al. 1999) suggests that actions of progesterone at the oxytocin cells in the hypothalamus may also be important for parturition. Classically, progesterone acts through specific intracellular receptors to regulate gene expression. However, metabolites of progesterone can also have membrane actions, and in particular, allopregnanolone can act at GABAA receptors to potentiate the actions of GABA, depending upon the particular subunit composition of the receptor. GABA is an important neurotransmitter for oxytocin cells about 45 % of all synapses onto them contain GABA, and the total number of GABA synapses in the supraoptic nucleus is substantially higher in lactating animals than in virgins (El Majdoubi et al. 1997). The GABA innervation appears to play a role in patterning the pulsatile discharge of oxytocin cells that is observed both during parturition and during suckling-induced reflex milk ejection (Moos, 1995; Voisin et al. 1995). Brussaard et al. (1999) recorded GABAA receptor-mediated spontaneous monoquantal inhibitory postsynaptic currents (sIPSCs) from rat supraoptic neurones in hypothalamic slices in vitro. They found a higher incidence of sIPSCs in pregnant rats than in virgin rats, consistent with the observations of an increase in the density of GABA-containing synaptic boutons. Importantly, the sIPSCs were markedly prolonged in the presence of allopregnanolone. Taking into account the frequency and amplitude of sIPSCs, the action of allopregnanolone and the hypertrophy of oxytocin neurones in lactation (reflected in increased capacitance), Brussaard et al. (1999) inferred that the effective GABAA receptor-mediated synaptic current density was much greater in pregnant rats than in virgin or lactating rats. Thus the collapse of progesterone production at term may abruptly reduce the effectiveness of GABA inhibition, and thereby enhance the excitability of oxytocin cells. Clearly this may be important during parturition, but the effect may not persist for long. Indeed, within a day the duration of sIPSCs is significantly longer in the absence of allopregnanolone, which now has no significant effect. This seems to be due to a rapid switch in the types of a subunits inserted into the GABAA receptors. By mid-lactation, a massive change in expression of GABAA receptor subunit mRNAs is apparent. With competitive polymerase chain reaction Brussaard and colleagues found that, while the expression of both a1 and a2 subunit mRNAs was increased, the ratio of a1 : a2 subunit mRNA expression was changed 8-fold in favour of a2 subunit mRNA. (ABSTRACT TRUNCATED)

Possible involvement of very low density lipoproteins in steroidogenesis in the human ovary.

To determine whether human luteal cells can utilize very low density lipoproteins (VLDL)-carried cholesterol for steroidogenesis, we investigated the expression of VLDL receptor mRNA in human ovarian tissues and progesterone production by human luteinized granulosa cells after the addition of VLDL. The production of progesterone in the presence of human chorionic gonadotrophin (HCG) was increased significantly (P < 0.05) by VLDL (2479 +/- 1477 ng/10(5) cells, mean +/- SD, n = 6) and low density lipoproteins (LDL) (2726 +/- 1287), in comparison with the level in the absence of these lipoproteins (1350 +/- 739). Northern blot analysis revealed that the levels of expression of VLDL and LDL receptor mRNA in granulosa cells were almost equal to those in whole ovarian tissue. VLDL receptor mRNA was abundant in granulosa cells of preovulatory follicles and cells of the corpus luteum. Preovulatory thecal cells and stromal cells expressed lower amounts of VLDL receptor mRNA than granulosa cells of preovulatory follicles and cells of the corpus luteum. From the present study, it might be suggested that VLDL is utilized for steroidogenesis in human luteinized granulosa cells.

Bone Health Is Not Affected by Luteal Phase Abnormalities and Decreased Ovarian Progesterone Production in Female Runners

Bone Health Is Not Affected by Luteal Phase Abnormalities and Decreased Ovarian Progesterone Production in Female Runners

Bone health is not affected by luteal phase abnormalities and decreased ovarian progesterone production in female runners.

The primary purpose of this study was to determine whether decreased ovarian progesterone production, associated with short and inadequate luteal phases in exercising women, was associated with decreased bone mineral density (BMD) and altered bone metabolism. Thirty-three eumenorrheic menstruating women participated in this study for 3 months. Subjects were required to collect daily urine samples for three consecutive menstrual cycles and have blood and urine collected weekly. Daily urine samples were analyzed for free LH, estrone conjugates (E1C), and pregnanediol 3-glucuronide (PdG), adjusted for creatinine, whereas weekly blood and urine samples were analyzed for bone markers, estradiol, progesterone, FSH, and LH. Based on the analyses of these samples, subjects were divided into three groups: sedentary ovulatory (SedOvul; n = 9), exercising ovulatory (ExOvul; n = 14), and exercising luteal phase defects (ExLPD; n = 10). The three groups were matched for age (27.6 +/- 1.0 yr), weight (60.6 +/- 1.9 cm), and reproductive maturity (14.5 +/- 1.0 yr), PdG production during the luteal phase was lower (P = 0.004) in the ExLPD women compared to that in the SedOvul group (2.4 +/- 0.4 vs. 5.1 +/- 0.6 ng/mL creatinine, respectively). The ExOvul group also had less (P < 0.01) PdG production during the luteal phase (3.5 +/- 0.3 ng/mL creatinine) compared to the SedOvul group. The total production of PdG, as assessed by area under the curve analysis, was also lower (P < 0.001) in the ExOvul and ExLPD groups compared to that in the SedOvul group. E1C production, however, was not different (P > 0.05) among the groups, except for E1C during the early follicular phase, which was lower (P = 0.043) in the ExLPD group than that in the SedOvul group. BMD and biochemical markers of bone metabolism were unaffected by and not associated with the compromised progesterone environment, but BMD values at the proximal femur (r = 0.354; P = 0.061) and total body (r = 0.359; P = 0.056) were associated with decreased early follicular E1C production. We conclude the following. 1) Luteal phase disturbances occur independent of training volume, and volume of training does not have to be severe to result in menstrual disturbances. 2) As a result of exercise, disturbance in progesterone production is not associated with decreased bone mass. 3) Long follicular phases are associated with reduced estrogen production during the early follicular phase, which are both associated with decreased bone mass. 4) Provided the estradiol status is adequately maintained, BMD is unaffected by decreased progesterone production associated with short and inadequte luteal phases in exercising women.

Toxicity of methoxyacetic acid in cultured human luteal cells.

Ethylene glycol monomethyl ether (EGME) and its proximate metabolite, 2-methoxyacetic acid (MAA), increase ovarian luteal cell progesterone production in the female rat in vivo and in cultured rat luteal cells in vitro, respectively. In order to better assess the potential hazard of EGME and MAA to women, these studies were conducted to determine whether the same concentrations of MAA increase progesterone in human luteinized granulosa cells as in rat luteal cells. Human cells were collected from healthy anonymous oocyte donors, washed, plated 25,000 viable cells per well, and treated with 10 IU hCG and 0-5 mM MAA for 6-48 hr. Progesterone in media was significantly elevated after 24 hr incubation at >/=1 mM MAA. MAA had no effect on ATP levels at 6 or 24 hr. Thus, MAA increased progesterone production in cultured human luteal cells at the same concentration as MAA increased progesterone in rat luteal cells. The implication is that EGME has the potential to alter ovarian luteal function in women. These data should be useful for determining the real health hazards and potential risks of EGME exposure.

Effects of Food Deprivation in Early Pregnancy on the Development of Ovaries and Adrenals in Female Progeny of the Water Vole ( Arvicola terrestris)

The effects of maternal food deprivation for 16 hr on day 3 and again on day 5 of pregnancy on the development of adrenals and ovaries in the female offspring during postnatal life (8, 21, 30 and 60 days after birth) were examined. Experimental and control groups consisted of 6–15 animals. On day 8, the daughters of the deprived mothers had lower body weight than the control animals. Later, the differences between the groups disappeared. Maternal food deprivation alters the prepubertal dynamics of adrenal progesterone production in vitro, and in mature experimental females adrenal progesterone production is significantly ( P < 0.05) lower than in the control. In deprived mothers' offspring, the postnatal development of the endocrine function of the ovaries was disturbed: on day 8, the ovarian progesterone production was 3.3 times less ( P < 0.001) and ovarian estradiol production was 3.2 times less ( P < 0.05) than in the control, and on day 30, a prepubertal peak in ovarian estradiol production in vitro was absent. Maternal food deprivation causes alterations in the prepubertal dynamics of blood concentrations of corticosterone, progesterone and estradiol and reduction in blood concentrations of progesterone ( P < 0.05) and estradiol ( P < 0.001) in mature individuals. It was concluded that maternal food deprivation before implantation disturbs the normal course of postnatal maturation of the ovarian endocrine functions and adrenal progesterone secretion in daughters.

Ketoconazole Impairs Early Pregnancy and the Decidual Cell Response via Alterations in Ovarian Function

Ketoconazole (KCZ) is an imidazole antifungal agent that also affects P450 enzymes of the mammalian steroidogenic system. Several steps in the ovarian steroidogenesis pathway are known to be inhibited by KCZ, but previous work has failed to address the ramifications of such inhibition with respect to early pregnancy. In initial studies, Holtzman rats (8–10/group) were administered 10–100 mg/kg KCZ during days 1–8 of pregnancy. On day 9, evaluations revealed a reduction at both 75 and 100 mg KCZ/kg in the number of implantation sites and serum progesterone levels as well as an increase in ovarian weight The decidual cell response (DCR) was blocked by KCZ in parallel with decreased serum progesterone and increased ovarian weight, indicating direct interference with uterine function. KCZ had no effect when given to long-term-ovariectomized rats that were hormone supplemented to permit the DCR, indicating that the ovary was at least one site of KCZ action on early pregnancy. Measurement of ovarian progesterone production in vitro from ovaries removed from rats treated in vivo with KCZ indicated a decline in progesterone production, suggesting a direct effect of KCZ on ovarian steroidogenesis. These data demonstrate that KCZ can compromise early pregnancy and appears to do so by inhibiting progesterone synthesis in the ovary.

Effect of RU486 on ovarian progesterone production at pro-oestrus and during pregnancy: a possible dual regulation of the biosynthesis of progesterone

Changes in progesterone production were analysed after intrabursal ovarian administration of the antiprogesterone RU486, mifepristone, in rats at pro-oestrus and during pregnancy. RU486 was administered at 09:00-10:00 h and serum progesterone was measured 8 h after treatment, except for those on days 3 and 12 of pregnancy when the steroid was measured 4, 8 and 24 h later. RU486 stimulates progesterone production on the day of pro-oestrus and on days 3-5 and 15-20 of pregnancy. Conversely, treatment with the antiprogestagen inhibits progesterone production on days 7-14 of gestation. The inhibition (day 12) or stimulation (day 19) of progesterone production induced by RU486 could be correlated with the simultaneous inhibition or stimulation of 3 beta-hydroxysteroid dehydrogenase (3 beta-HSD) activity observed in corpora lutea. A similar effect on 3 beta-HSD activity in corpora lutea was obtained by intrabursal ovarian administration of a specific progesterone antibody, indicating that the effect of RU486 is exerted through its antiprogesterone action. On the day of pro-oestrus and during early pregnancy the intrabursal ovarian injection of RU486 did not modify serum prolactin and LH concentrations, demonstrating that the antiprogesterone did not have a central action. The stimulatory action of RU486 on progesterone production on days 3 and 5 of pregnancy shifted to an inhibitory effect on progesterone production on day 7. Oestradiol treatment on day 6 of pregnancy reversed the effect of RU486 on progesterone production on day 7, inducing a response similar to that obtained on days 3 and 5 of gestation.(ABSTRACT TRUNCATED AT 250 WORDS)

Superoxide dismutase activity, lipid peroxide production and corpus luteum steroidogenesis during natural luteolysis and regression induced by oestradiol deprivation of the ovary in pseudopregnant rabbits.

The relationship of oxygen free radicals to corpus luteum function in rabbits was explored during various stages of pseudopregnancy, including natural and induced luteal regression. Induced luteolysis was achieved during mid-pseudopregnancy by removal of an oestradiol capsule placed at the onset of pseudopregnancy, which suppressed ovarian oestradiol production. Activity of manganese superoxide dismutase (Mn SOD) was significantly and positively correlated with ovarian progesterone production (P < 0.01) throughout pseudopregnancy and during natural regression. Oestradiol deprivation for 12, 24 or 72 h resulted in declines in Mn SOD activity and progesterone secretion, although Mn SOD rose and corpus luteum steroidogenesis was restored to normal when the capsule was replaced for 48 h before assessment, having been removed for 24 h. Lipid peroxide and progesterone concentrations were not correlated, although a significant rise in lipid peroxides in the luteal tissue was detected after deprivation of oestradiol for 72 h. Changes in progesterone production and Mn SOD activity were not associated with alterations in concentration of prostaglandin F metabolite. These data suggest that Mn SOD may be involved in regulating function of the corpus luteum during pseudopregnancy in rabbits and that oxygen free radicals may play a role in regression of corpus luteum in this species.

Some Characteristics of Small White Ovarian Follicles: Implications for Recruitment and Atresia in the Domestic Hen

Granulosa cells from resting or slow-growing follicles that have yet to enter the preovulatory hierarchy (1to 8-mm in diameter) of the hen ovary are steroidogenically incompetent. The inability of granulosa tissue to synthesize the steroid precursor, pregnenolone, is due to the absence of cytochrome P450 side-chain cleavage (P450scc) enzyme activity. Cytochrome P450scc mRNA levels and enzyme activity can be induced in granulosa cells collected from 6to 8-mm follicles, in vitro, by pretreatment with agents that induce cyclic adenosine monophosphate (cAMP) formation (e.g. forskolin, FSH). Prior and up to the 6to 8-mm stage of development, the theca layer is solely responsible for ovarian progesterone, androgen and estrogen production; such steroidogenesis is under the regulatory control of pituitary gonadotropins (LH and, to a lesser extent, FSH). Spontaneous atresia is common in follicles 3to 5-mm in diameter, and is functionally characterized by the activation of a nuclear endonuclease that cleaves genomic DNA into a series of 185-b.p. fragments and ultimately results in resorption of the follicle. We propose that this process (termed apoptosis) also mediates ovarian regression at the termination of the breeding period in seasonally-breeding birds.

Contraceptive Development Lags in U.S.

Contraceptive development in the US has been halted by all but one company Ortho Pharmaceuticals. The reasons for this are complex and the problem is very serious. Legal and regulatory pressures have taken away the incentive to do research. There are 3 million unwanted pregnancies each year in this country. If contraceptive use were more widespread and the technology was constantly being improved by a highly competitive market, then this number would be much lower. There are several new forms of birth control being studies for use in the US, such as injectables using microspheres or microcapsules which can last for 1, 3, or 6 months, biodegradable pellets that are inserted under the skin of the hip or upper arm slowly release hormones, the vaginal ring which is saturated with time-released hormones and is worm around the opening of the uterus like a diaphragm, transdermal patches which are changed weekly for 3 weeks with a placebo patch to allow menstruation, osmotic pills which gradually release hormones on a lower and less frequent schedule, and vaccines which can immunize women against hormones in the placenta, egg or from sperm. This research is at an early stage. Luteinizing hormone-releasing hormone (LHRH) analogues suppress ovulation by affecting the pituitary gland. This method has the side effect of blocking ovarian production of estrogen and progesterone. Male methods like Inhibit inhibit the production of follicle-stimulating hormone (FSH). Gossypol has been used in China, but one side effect is that it is sometimes irreversible. Outside the US the injectables Depo-Provera and Noristerat are approved in 90 and 40 countries respectively. Norplant is a progesterone releasing implant, made in Finland, that lasts up to 5 years; it was recommended for approval in 1989 by the FDA's Fertility and Maternal Health Drug Advisory Committee RU-486 prevents the cells in the uterus from receiving progesterone, was developed in France. The Filshie clip is a titanium and silicone rubber barrier that blocks the fallopian tubes. Ovablock is a silicone plug that blocks the fallopian tubes and increase reversibility.

Effects of dibutyryl cyclic AMP on oocyte maturation and ovulation in the perfused rabbit ovary

The involvement of cyclic AMP (cAMP) in mammalian oocyte maturation was assessed using cultures of rabbit cumulus-oocyte complexes and in-vitro perfused rabbit ovaries. Rabbit cumulus-oocyte complexes were cultured in Brackett's medium with or without dibutyryl cyclic AMP [Bu)2cAMP) at 10(-3), 10(-4) or 10(-5) M for 4-12 h. At 4 h spontaneous meiotic maturation was significantly inhibited by (Bu)2cAMP (P less than 0.025). With prolonged incubation, spontaneous maturation progressed despite exposure to (Bu)2cAMP. When ovaries were continuously perfused in vitro for 12 h with (Bu)2cAMP (10(-3) M) or medium alone, (Bu)2cAMP stimulated ovarian progesterone production, but did not affect ovulation or maturation of follicular oocytes. When ovaries were perfused in vitro with or without (Bu)2cAMP (10(-3), 10(-4) or 10(-5) M) for the first 2 h and then transferred to medium without (Bu)2cAMP for an additional 10 h, ovulation did not occur, but transient exposure to (Bu)2cAMP stimulated a dose-related increase in maturation of follicular oocytes. Degeneration of follicle-enclosed oocytes and cumulus-oocyte complexes was not affected by exposure to (Bu)2cAMP. These results suggest that transient, but not continuous, elevation of cAMP after the gonadotrophin surge may be required for the initiation of oocyte maturation.

Role of arachidonic acid in luteinizing hormone-releasing hormone action: stimulation of progesterone production in rat granulosa cells.

This study investigates the hypothesis that stimulation of ovarian progesterone (P) production by LHRH is mediated in part by arachidonic acid (AA). In rat granulosa cells prelabeled with [3H]AA or [3H]inositol, treatment with LHRH stimulates the accumulation of radiolabeled inositol phosphosphates, diacyglycerol, and unesterified AA. Treatment with AA (3 X 10(-7)-10(-5) M) enhances P production in a dose-dependent manner. Concurrent treatment with AA and LHRH (or a LHRH agonist) further stimulates P production. The stimulatory effect of AA on P production, either alone or in combination with LHRH, could be seen as early as 3 h after AA addition. Addition of a phorbol ester, 12-O-tetracecanoylphorbol-13-acetate (TPA), to granulosa cells stimulates P production. Interestingly, the concomitant presence of AA and TPA further enhances production compared with either TPA or AA treatment alone. The stimulatory effect of AA on P production is completely abolished by nordihydroguaiaretic acid, but not by indomethacin. On the other hand, addition of nordihydroguaiaretic acid (but not indomethacin) reduces LHRH-stimulated P levels by about 50%. Nordihydroguaiaretic acid, as well, markedly attenuates the P response due to combined treatment with LHRH and AA. Taken together, these results strongly support the notion that AA (or its lipoxygenated metabolites) partially mediates the action of LHRH. Along with the calcium and protein kinase-C pathways, AA metabolism may be involved in the biological actions of LHRH in the ovary.