Effects of polyamines upon capacitation and fertilization in the guinea pig

The effects of polyamines upon the ability of guinea pig spermatozoa to undergo the acrosome reaction and upon sperm-egg fusion were investigated. All of the polyamines (polyarginines and compound 48/80) stimulated the occurrence of the acrosome reaction, although differences in the duration of the preincubation period required were noted. The stimulatory effect of the polyarginines could not be reversed by washing, while that of 48/80 was abolished by its removal prior to induction of the acrosome reaction. Polyarginine-treated spermatozoa were fully capable of fertilizing intact guinea pig eggs. In contrast, 48/80 completely blocked sperm-egg fusion at only 5-10 micrograms/ml. This inhibition was reversible by washing either treated gamete. The ability of polyamines which may also be present at the time and site of fertilization, in vivo, to inhibit or stimulate gamete functions or interactions is discussed.

Interactions of a phosphodiesterase inhibitor, 3-isobutyl-1-methyl xanthine, with prostaglandin E2, follicle-stimulating hormone, luteinizing hormone, and dibutyryl cyclic 3',5'-adenosine monophosphate (cAMP) in cAMP and steroid production by neonatal rat ovaries in vitro

The development of responsiveness to prostaglandin E2 (PGE2), FSH, LH, and [Bu]2cAMP was examined in whole ovaries isolated from neonatal Sprague-Dawley rats on days 0 (birth), 2, 4, or 6 postpartum. Pairs of ovaries were incubated with these stimuli in the absence or presence of 3-isobutyl-1-methyl xanthine (MIX), a potent phosphodiesterase inhibitor, and accumulations in the medium of cAMP, androstenedione, and estradiol were measured. PGE2 stimulated marked cAMP accumulation on day 0 whereas similar responses to FSH and LH did not develop until days 2 and 4, respectively. No cAMP accumulation was detectable in the absence of MIX. Ovaries gradually acquired the ability to produce both cAMP and steroids in response to FSH and LH over the first postnatal week. No steroid accumulation was measurable in incubations conducted on days 0 or 2; however, steroidogenesis was stimulable in day-4 ovaries by (Bu)2cAMP. PGE2, FSH, and LH also stimulated steroid accumulation on day 4, but only when MIX was present in the incubation, suggesting that high levels of endogenous cAMP can also lead to steroid production. By day 6, all stimuli elicited steroid accumulation in a dose-dependent fashion. MIX potentiated the responses to lower doses of these stimuli but not to the higher doses at this age. In the absence of MIX, LH was approximately 100 times more potent than FSH in stimulating steroid production; however, the two gonadotropins were nearly equipotent in this regard when MIX was present in the incubation. These results support the notion that a cAMP-sensitive steroidogenic apparatus is present in the rat ovary as early as the fourth day postpartum. Because of the marked effects of MIX on gonadotropin-induced steroidogenesis, it may be that modulation of phosphodiesterase activity is one way by which steroidogenesis is regulated in the neonatal rat ovary.

Androgen inhibition of FSH-stimulated progesterone production by granulosa cells of prepubertal pigs

Androgens have been reported to stimulate progesterone production by granulosa cells of several species, and to act synergistically with FSH in stimulation of progesterone accumulation by rat granulosa cells. Studies were undertaken to examine the effect of androgens on FSH-stimulated progesterone production in culture by granulosa cells derived from prepubertal pig ovaries. When included in 24-h culture with FSH, both androstenedione and testosterone caused a reduction in progesterone accumulation, but dihydrotestosterone and androsterone did not. Granulosa cells were cultured for 24 h with FSH and [14C]progesterone with or without testosterone; testosterone did not affect the rate of overall metabolism of [14C]progesterone and it was therefore concluded that testosterone inhibited progesterone synthesis, rather than enhancing its catabolism. 17 beta-Estradiol also inhibited FSH-stimulated progesterone accumulation. To determine whether the action of testosterone was mediated by conversion to estradiol, granulosa cells were cultured with FSH and testosterone with or without an aromatase inhibitor (4-acetoxy-androstenedione). The aromatase inhibitor failed to prevent the testosterone-induced reduction in progesterone accumulation, although it markedly inhibited estradiol accumulation. These results indicate that theca-derived androgens can inhibit FSH-stimulated progesterone production by granulosa cells in the prepubertal pig, independently of estradiol.

Site of action of androgens on follicle-stimulating hormone-induced aromatase activity in cultured rat granulosa cells

This paper describes experiments on cultured granulosa cells isolated from ovaries of immature rats designed to locate the site of action of androgens on FSH-induced aromatase activity. Treatment of cells during a 36-h induction period with (Bu)2cAMP, 8- BrcAMP , FSH, prostaglandin E2, or cholera toxin resulted in induction of aromatase activity measured as 17 beta-estradiol accumulation during a 6-h test period with testosterone (5 X 10(-7) M) added to medium as substrate. Presence of testosterone (5 X 10(-7) M) during the induction period enhanced the effects of FSH, cholera toxin, and prostaglandin E2 on aromatase activity, but not those of the cAMP analogs. The effects of culturing and steroids on responsiveness of granulosa cells to FSH (measured as FSH-stimulated cAMP production during a 1-h test period) were examined. The data showed that culturing in medium alone for 36 h resulted in a decrease in the ability of FSH to stimulate cAMP production when compared to that of freshly isolated cells. After culture with testosterone (5 X 10(-7) M), dihydrotestosterone (DHT) (5 X 10(-7) M), or 17 beta-estradiol (5 X 10(-7) M), responsiveness was at least partially restored. After treatment with progesterone (5 X 10(-7) M), FSH stimulation of cAMP production was not significantly different from that of cells cultured in medium alone. Hydroxyflutamide (5 X 10(-5) M), an antiandrogen known to block androgen-receptor interaction, abolished the effect of DHT and depressed the effect of testosterone on responsiveness of granulosa cells to FSH. Cells treated for 36 h with testosterone (5 X 10(-7) M) bound significantly more [125I]iodo-FSH than cells cultured in medium alone. Although DHT (5 X 10(-7) M) slightly increased FSH binding, the effect was not statistically significant. These results suggested that androgens regulate granulosa cell aromatase activity not only as substrates, but also by acting at a site before cAMP production (possibly at the level of the FSH receptor) in the control of FSH-induced enzyme activity.

Intrauterine insemination enhances fertility of frozen semen in superovulated ewes

Superovulated ewes were inseminated with fresh or frozen semen in a factorial experiment which compared two techniques of artificial insemination; i.e. conventional cervical deposition and intrauterine deposition at laparoscopy. Similar fertilization rates resulted from insemination with fresh semen at cervical (81% of ova from 11/11 ewes) and intrauterine (83% of ova from 10/12 ewes) sites. These results approached those observed in a naturally-mated group (95% of ova from 5/5 ewes). In ewes inseminated with frozen semen, fertilization rate was markedly reduced (P less than 0.05) after cervical insemination (11% of ova from 3/11 ewes) and partly restored (P less than 0.05) after intrauterine insemination (50% of ova from 8/11 ewes).

Reduction of sperm transport in ewes by superovulation treatments

Oestrus was synchronized in ewes by (a) withdrawal of an intravaginal progestagen sponge after 12 days or (b) injection of PGF-2 alpha on Day 11 of the oestrous cycle. In addition, ewes were treated with (a) no hormone, (b) 1500 i.u. PMSG 48 h before sponge removal or PG injection, or (c) 24 mg porcine pituitary FSH in multiple injections commencing 48 h before sponge removal or PG injection, in a 2 X 3 factorial design. Ewes were inseminated with 0.2 ml fresh undiluted semen into the neck of the cervix 48 h after sponge removal or PG injection. Normally cyclic ewes were similarly inseminated within 12 h of observed standing oestrus. At 24 h after insemination one uterine horn and one oviduct were flushed for recovery of spermatozoa and ova. When compared with naturally cyclic ewes, PG synchronization resulted in a marked reduction in the numbers of spermatozoa recovered (P less than 0.05), and sponge synchronization led to a small, non-significant, reduction. Within the synchronized ewes, PMSG and FSH resulted in an equivalent superovulatory response, but there was a marked reduction in sperm recovery when compared with unstimulated animals (P less than 0.01), with the greatest reduction attributable to PMSG treatment. Spermatozoa were recovered from fewer ewes treated with PMSG than with FSH (P less than 0.05). Despite the observed impairment of sperm transport, a high fertilization rate was observed within each group and there were no differences between treatments.

Reduction in fertilization rate in vitro of oocytes from immature rats induced to superovulate

Immature female rats (65-70 g) were injected with 4 i.u. PMSG (control) or superovulated with 8, 16, 24 or 40 i.u. PMSG and were killed 68-70 h later, shortly after the normally expected time of ovulation. Oocytes were recovered from the oviducts and inseminated in vitro. After 18 h oocytes were counted and classed as degenerate or 1-cell. Mean numbers of oocytes recovered were 8.2, 26.8, 50.7, 38.7 and 38.5 for each dose of PMSG respectively. The 1-cell oocytes were assessed for sperm penetration of the vitellus and pronuclear development and later for development to the 2-cell stage. Fertilization rates at the 1-cell stage were 76.8, 62.9, 53.6, 52.2 and 44.5% for the rats treated with 4, 8, 16, 24 and 40 i.u. respectively (P less than 0.001). On average, 91% of fertilized 1-cell oocytes developed to the 2-cell stage and there was no difference between treatments in this respect. Significantly more of the unfertilized oocytes were degenerate in the rats treated with 24 or 40 i.u. PMSG (34.6 and 50.4%) than in those treated with 4, 8 or 16 i.u. (7.0, 13.9, and 7.5%) (P less than 0.001). When rats were killed 63-65 h after PMSG, just before the normally expected time of ovulation, some of the rats treated with 24 and 40 i.u. PMSG had partly ovulated: of the oocytes recovered from the oviducts only 12.3% (24 i.u.) and 26.6% (40 i.u.) were fertilized. These results demonstrate that proportionately fewer oocytes recovered from superovulated rats are competent to undergo in-vitro fertilization than are oocytes recovered from control rats.

Site of androgen inhibition of follicle-stimulating hormone-stimulated progesterone production in porcine granulosa cells

In granulosa cells derived from medium-sized porcine follicles, certain androgens have been shown to inhibit FSH-stimulated progesterone synthesis. To determine the site at which this inhibition takes place, the effects of androgens on FSH- and (Bu)2cAMP-stimulated pregnenolone and progesterone syntheses were examined. Granulosa cells were isolated from 4- to 6-mm follicles and cultured for 24 h in modified Eagle's Minimum Essential Medium, alone or with FSH (1 microgram/ml) or (Bu)2cAMP (0.5-4 mM) in the presence or absence of androstenedione or testosterone. (Bu)2cAMP stimulated progesterone production in a dose-dependent manner. Testosterone (5 microM) had a slight, but nonsignificant, inhibitory effect on basal progesterone production, but significantly inhibited the synthesis of progesterone in the presence of (Bu)2cAMP, suggesting that testosterone inhibits progesterone synthesis at a step distal to cAMP formation. In the absence of FSH, granulosa cells produced substantial quantities of pregnenolone. FSH caused a 3-fold stimulation of pregnenolone synthesis. The addition of androstenedione or testosterone (5 microM) markedly increased pregnenolone accumulation in FSH-treated cultures. To determine at what step androgens affected FSH-stimulated pregnenolone production, granulosa cells were cultured with (Bu)2cAMP and/or testosterone for 24 h. (Bu)2cAMP stimulated pregnenolone synthesis in a dose-dependent manner. Testosterone (5 microM) significantly increased pregnenolone synthesis in response to (Bu)2cAMP, suggesting that androgens acted at a step distal to cAMP formation. Since these concentrations of androgens markedly inhibited FSH-stimulated progesterone production by these preparations, these results suggest that androgens may affect the conversion of pregnenolone to progesterone.

Changes in relaxin production by the theca during the preovulatory period of the pig

Theca and granulosa layers were isolated from the preovulatory follicles of prepubertal gilts which were untreated (Group A), killed 72 h after 1000 i.u. PMSG (Group B), killed 84 h after PMSG (Group C), or killed 84 h after PMSG + 500 i.u. hCG given at 72 h (Group D). The tissues from individual follicles were cultured for 24 h alone (C), with FSH (F) or with LH (L), and the content of immunoreactive relaxin in the culture media was measured by RIA. Concentrations of relaxin-like material were close to the limit of detection of the assay in all granulosa cell cultures, and in the thecal cultures from the untreated gilts. However, thecal cultures from all 19 treated gilts produced relaxin. The mean +/- s.e.m. concentrations (pg/follicle) in Groups AC, BC, CC and DC were 26 X 5 +/- 3 X 04, 93 X 1 +/- 4 X 6, 138 +/- 16 X 4 and 285 X 6 +/- 54 X 1 respectively. Therefore relaxin production was stimulated by PMSG (P less than 0 X 05), with hCG treatment in vivo leading to a further significant increase (P less than 0 X 05). In-vitro treatment with gonadotrophins had no effect in Groups A, C and D, but in Group-B gilts LH produced a significant (P less than 0 X 05) rise in relaxin levels. These studies indicate that the theca is the principal source of relaxin in the porcine preovulatory follicle. The increased production before ovulation suggests that relaxin may be involved in follicular growth or rupture.

Porcine follicular fluid does not inhibit maturation of rat oocytes in vitro

Follicular fluid from small-(1-2 mm) or medium-(3-8 mm) sized pig follicles was collected under conditions designed to minimize possible alteration or degradation of native fluid components. The effects of follicular fluid with or without benzamidine, an inhibitor of proteolytic activity, on oocytes collected 20 or 44 h after PMSG treatment of rats were examined. A follicular fluid fraction of Mr less than 10 000 (PM-10 membrane filter) was also tested. Follicular fluid from small- and medium-sized follicles and control medium alone supported maturation of oocytes collected 20 or 44 h after PMSG, but follicular fluid (50%) from medium-sized follicles containing 5 X 0 mM-benzamidine significantly inhibited oocyte maturation. Comparable inhibition was also observed with medium containing 5 X 0 mM-benzamidine. The PM-10 filtrate failed to inhibit oocyte maturation as assessed by germinal vesicle breakdown but did significantly inhibit first polar body formation and therefore restricted the extent of maturation. The results indicate that native pig follicular fluid is unable to inhibit the initiation of maturation of rat oocytes in vitro.

Formation of androgen conjugates by porcine granulosa cells

The relative abilities of isolated and recombined theca and granulosa cells, derived from medium-sized porcine ovarian follicles, to synthesize androgens and estrogens were compared. Isolated thecal preparations produced large amounts of immunoreactive androstenedione and testosterone. When theca was co-cultured with granulosa cells, accumulation of both these androgens was markedly less. Though the co-cultures produced significantly higher amounts of estradiol, this increase did not account for the reduced androgen production. To determine if the lesser androgen accumulation in the combined cultures was due to metabolism by granulosa cells of androgens to other metabolites, the fate of [3H]androstenedione or [3H]testosterone was followed. Whenever granulosa cells were present in the incubation dishes, most of the radioactivity remained in the aqueous fraction after ether extraction. Examination of the aqueous fraction by DEAE-Sephadex A25 demonstrated the presence of androgen sulphates. The results suggest that granulosa cells are the site at which follicular formation of androgen sulphates takes place.

Prostanoid content of human milk: relationships to milk fatty acid content

Analysis of human milk was conducted to determine if transitions in milk lipid composition and thus the changes in fatty acid synthesis that occur during lactogenesis are related to levels of specific prostanoids present in milk lactated. Serial samples representative of a complete expression and reflecting varying concentrations of milk fatty acids were collected over the first 37 days of lactation. Milk from mothers delivering infants at term and mothers delivering premature infants of 28-33 weeks gestational age was compared to examine potential relationships between prostanoid concentration and gestational age effects on milk lipid content. Milk levels of prostaglandin E, prostaglandin F and the metabolite of prostacyclin--6-keto-prostaglandin F1 alpha were determined by radioimmunoassays. Transitions in fatty acid content for all milk lipid classes were determined by quantitative analysis of fatty acids by glass capillary gas liquid chromatography. During lactation the levels of prostaglandin E correlated with milk content of 6-keto prostaglandin F1 alpha. For term mothers, milk content of prostaglandin E, 6-keto prostaglandin F1 alpha, total fatty acids and medium chain fatty acids increased from early lactation when compared with subsequent days sampled. Levels of these milk constituents observed for early milk of preterm mothers were significantly different when compared with term mothers and in addition did not follow the same longitudinal pattern during subsequent days of lactation. Physiologically significant levels of prostaglandins in milk may reflect the balance between hormonal and subcellular controls over lactogenesis. It is also conceivable that the presence of these prostanoids in milk may influence gastrointestinal physiology and nutrient absorption in the neonate.

Changes in responsiveness of rat granulosa cells to prostaglandin E2 and follicle-stimulating hormone during culture

The changes in responsiveness of granulosa cells to either FSH or prostaglandin E2 (PGE2), during culture of the cells, have been examined. In freshly isolated cells, FSH and PGE2 stimulated both cyclic AMP and progesterone production in a dose-dependent manner. In these cells, FSH stimulated cyclic AMP production to a greater extent than did PGE2. After the cells had been cultured for 2 days, neither FSH nor PGE2 stimulated progesterone production to any detectable extent. In these cells the ability of FSH to stimulate cyclic AMP was decreased, and that of PGE2 was increased markedly, such that PGE2 was far more effective than FSH in stimulating cyclic AMP. After culture of the cells for a further 2 days (4 days total), the FSH stimulation of cyclic AMP returned to that seen in freshly isolated cells, whereas the stimulation by PGE2 remained elevated. The acute stimulation of progesterone production could be restored by chronic exposure of the cells to either FSH or PGE2. These results demonstrate that dramatic changes in responsiveness of granulosa cells take place during culture. The results also suggest that some stimulating factor must be present to maintain the steroidogenic capabilities of the cells. Without this, although the cells are able to produce cyclic AMP in response to FSH, they cannot produce progesterone.

Granulosa cell stimulation of thecal androgen synthesis

The role of granulosa cells on porcine follicular androgen synthesis was studied. Granulosa cells were cultured for 24 h either in Eagle's minimum essential medium (MEM) or in MEM plus follicle-stimulating hormone (FSH; 1 microgram/mL). Thecal preparations were cultured with or without luteinizing hormone (LH), either in MEM, 50% "spent media" from granulosa cells control (MA) or 50% "spent media" from granulosa cells incubated with FSH (MB). In the absence of LH, MB stimulated accumulation of both delta 4-androstenedione (twofold) and testosterone (threefold). MB was found to contain high levels of C21-steroids, including progesterone and material which behaves chromatographically and immunologically like pregnenolone. These amounts of C21-steroids were able to stimulate thecal androgen production. The results suggest that granulosa cells contribute to thecal androgen production by providing steroid substrate. This would provide a means for granulosa cells to control the availability of aromatizable androgens.

Involvement of estrogens in the regulation of granulosa cell aromatase activity

Androgens have been shown to enhance follicle-stimulating hormones (FSH) induced aromatase activity in cultured granulosa cells obtained from the ovaries of immature rats, however, aromatizable androgens are more effective than nonaromatizable androgens. The present study was designed to investigate the possibility that aromatization of androgens to estrogens is responsible for the greater effectiveness of aromatizable androgens. Granulosa cells were cultured during a 36-h induction period in the presence of FSH, FSH + testosterone, or FSH + dihydrotestosterone with or without 4-acetoxy-4-androstene-3,17-dione (4-acetoxy-A), an inhibitor of aromatase activity. Treatment with androgens enhanced aromatase activity measured as accumulation of estradiol-17 beta during a 6-h test period with testosterone added as substrate. The effects of both androgens on FSH-induced aromatase activity were blocked by 4-acetoxy-A. Presence of a high concentration of diethylstilbestrol (DES), a synthetic estrogen, during the induction period had a significant positive effect on FSH-induced estradiol-17 beta accumulation during the test period. All lower doses were ineffective. Nafoxidine, an antiestrogen known to inhibit binding of estrogens to their intracellular receptors, had no effect on enhancement of FSH-induced aromatase by testosterone. The results of these experiments suggest that estrogens synthesized by granulosa cells in culture are only partially responsible for the greater ability of testosterone to enhance FSH-induced aromatase activity compared with that of dihydrotestosterone (DHT). Other factors such as differential rates of androgen metabolism and receptor affinities are probably the major determinants of androgen potency.

Endocrine responses of goats after induction of superovulation with PMSG and FSH

Goats in Group A were pretreated for 9 days with a synthetic progestagen, administered via intravaginal sponge, and 1000 i.u. PMSG s.c. on Day 12 of the oestrous cycle. Goats in Group B had the same PMSG treatment, but not the progestagen pretreatment. Group C goats received a s.c. twice daily injection of a porcine FSH preparation (8 mg on Day 12, 4 mg Day 13, 2 mg Day 14 and 1 mg Day 15). Oestrus was synchronized in all animals by 50 micrograms cloprostenol, 2 days after the start of gonadotrophin treatment. The vaginal progestagen sponges were removed from Group A at the same time. Mean ovulation rate was slightly higher in FSH-treated than in the PMSG-treated animals, whereas the incidence of large follicles that failed to ovulate was significantly elevated in PMSG-treated animals in Group B. More goats in Groups A and B than in Group C exhibited premature luteal failure. Progestagen pretreatment appeared to suppress both follicular and luteal activity, as indicated by numbers of large non-ovulating follicles and by the magnitude and duration of elevated plasma oestradiol levels following PMSG stimulation, and by decreased plasma progesterone levels before and after PMSG treatment. Oestrogenic response to FSH was considerably less than that to PMSG, as indicated both by a considerably shorter duration of elevation of circulating oestradiol levels during the peri-ovulatory period, and by lower maximal oestradiol levels. Differences in the ovarian responses to PMSG and FSH may be attributed primarily to differences in the biological half-life of each preparation.

Oocyte normality after superovulation in immature rats

The developmental ability of oocytes recovered from superovulated immature rats (40 i.u. PMSG) was compared with that of oocytes from control rats (4 i.u. PMSG). Oocytes were collected from the oviducts immediately after ovulation or from large follicles, and were transferred to one ovarian bursa of normal adult recipients. Fertilization and subsequent fetal development occurred in the recipients which were killed on Day 20. The proportions of oocytes surviving after transfer from the oviducts of donors which received 4 or 40 i.u. PMSG or from the follicles of those which received 40 i.u. PMSG were not significantly different. However, the proportion of oocytes surviving after recovery from the follicles of donors receiving 4 i.u. PMSG was significantly higher (P less than 0.05). These studies suggest that oocytes recovered from superovulated or control rats are equally able to develop, and the failure to maintain pregnancy that has been reported for superovulated rats in previous studies is not attributable to defects in the oocytes.

Superovulation treatments and embryo transfer in Angora goats

A high incidence of early luteal regression after PMSG superovulation was associated with low recovery of embryos from reproductive tracts of Angora goats flushed later than Day 5 after onset of oestrus. Embryos were successfully recovered (mean 7.9/female) by flushing on Days 2-5. Mean ovulation rate after an FSH regimen (16.1 +/- 0.8) was significantly higher than that after a single injection of PMSG (10.8 +/- 1.2). Fertilization rate and survival of embryos following transfer to naturally synchronized recipient feral goats did not differ between the two gonadotrophin regimens: the mean number of kids born to 47 donors treated with FSH (7.5 +/- 0.6) was significantly greater than that to 28 donors treated with PMSG (4.8 +/- 0.6). Irrespective of hormonal treatment, the numbers of embryos recovered and of kids born were correlated with ovulation rate (r = 0.82, P less than 0.001 for both). Embryo survival was influenced by ovulation rate in recipients, with 52%, 63% and 75% of transferred embryos being carried to term by recipients with 1,2 and 3 CL, respectively (P less than 0.01). More embryos survived (65%) when 2 embryos were transferred to each recipient than when 1 (51%) or 3 (48%) were transferred. In recipients receiving 2 embryos, survival was significantly improved by transfer of both embryos to the same oviduct (70%) than when one was transferred to each oviduct (62%). The percentage survival of embryos was optimal when oestrus of recipients was synchronized within +/- 1 day of oestrus in donors.

Production of prostaglandins by porcine preovulatory follicular tissues and their roles in intrafollicular function

Prostaglandin production in vitro by theca and granulosa cells isolated from prepubertal pig ovaries was quantified in order to investigate the role of prostaglandins in intrafollicular function. Prepubertal gilts were slaughtered without treatment (O h, control) or treated with 1000 IU pregnant mare's serum gonadotropin (PMSG) and slaughtered at 36 or 72 h, or at 75 h following treatment with 500 IU of hCG at 72 h. Theca and granulosa cells were isolated from preovulatory follicles and cultured for 24 h alone or with follicle-stimulating hormone (FSH) or luteinizing hormone (LH). In vitro accumulation of 6-keto-prostaglandin F1 alpha (6-keto-PGF1 alpha), prostaglandin E2 (PGE2) and prostaglandin F2 alpha (PGF2 alpha) was measured by radioimmunoassay. On a per follicle basis theca produced more of each prostaglandin (approx. 10-fold) than granulosa at each stage of follicular development; production by each tissue type increased with development of the follicle, responding to administration of gonadotropin (PMSG) in vivo. Neither tissue type was generally responsive to further gonadotropin stimulation in vitro. However, production of PGE2 by granulosa cells was increased by addition of gonadotropin, particularly LH, in vitro, with the greatest response observed in tissue obtained at 36 and 72 h after PMSG. There were no functional correlates between prostaglandin production and steroidogenesis by either tissue type and we conclude that prostaglandins do not have an obligatory role in follicular steroidogenesis. However, these data provide additional circumstantial evidence for a role of PGE2 in granulosa cell luteinization, and possibly in ovulation. The data also indicate that prostaglandins derived from thecal tissue in relatively large quantities may play an important role in ovulation.

Ovulation response and fertilization failure in immature rats induced to superovulate

Immature female rats (75 g body wt, aged 29 days) were injected with 4 or 40 i.u. PMSG on Day -2 and were killed at intervals between 18:00 h on Day -2 and 09:00 h on Day 1. Control animals (4 i.u.) ovulated between 00:30 and 05:30 h on Day 1 whereas the number of ova recovered from superovulated rats (40 i.u. PMSG) increased slowly between 06:00 h on Day -1 and 24:00 h on Day 0 and markedly between 24:00 on Day 0 and 06:00 on Day 1. Similarly treated rats were caged overnight on Day 0 with males of proven fertility and killed between 14:00 and 16:00 h on Day 1. A significantly lower percentage of normal 1-cell ova was recovered from the superovulated rats compared to control animals (71.6 and 98.5%) and of these 1-cell ova a lower percentage was fertilized (69.7 and 99.1%). In the control group all mated animals had a high proportion of ova fertilized whereas 26% of superovulated rats had none or a very low proportion fertilized. In the control animals there was evidence of sperm penetration and pronucleus formation; in superovulated rats significantly fewer ova had pronuclei than were penetrated. These results suggest that reduced fertility of superovulated immature rats is due to complete or partial failure of fertilization in some animals. The extended period during which ovulation occurs may be a contributory factor.

Implantation and later fetal development in immature rats given a superovulatory dose of pregnant mare's serum gonadotropin, later neutralized by antiserum

In an earlier experiment, 29-day-old female rats were superovulated with 40 IU pregnant mare's serum gonadotropin (PMSG) and very few blastocysts were recovered from the uterus on Day 5. Administration of a PMSG antiserum (a/s) prior to ovulation resulted in recovery of blastocysts in all rats and the present set of experiments was undertaken to investigate the later development of these blastocysts. Implantation was found to occur in only approximately 50% of superovulated (SOV) a/s-treated animals regardless of whether or not estrogen was given on Day 4. It is suggested that the exposure to high preovulatory estrogen and an imbalance in the progesterone/estrogen ratio during the early preimplantation period are possible causes of the loss of blastocysts. The majority of SOV a/s-treated rats in which implantation occurred carried fetuses to Day 20, although there was a further small loss of pregnancy between Days 8 and 20. On Day 8 steroid concentrations in both serum and ovaries were similar to those observed on Day 5 in earlier experiments. By Day 20 serum and ovarian progesterone concentrations were significantly higher than on Day 8 in all superovulated rats, which may reflect increased production by the larger number of corpora lutea in these animals. The present set of experiments shows that in a significant percentage of SOV a/s animals blastocysts are capable of implanting and continuing to develop into normal fetuses by Day 20. However, at least 50% of SOV a/s-treated rats fail to maintain pregnancy between Days 5 and 8 and this could be a result of a failure in the uterus to provide a suitable environment for implantation or to abnormalities in the blastocysts.

PGE2 and dibutyryl-cAMP enhance the response of rat granulosa cells to FSH

Granulosa cells isolated from immature Sprague-Dawley rat ovaries produce progesterone (31.7 pg/micrograms cell protein) in response to an acute FSH stimulus (5 micrograms/ml NIH-FSH-S11, 2 H). After culture for 48 h in the absence of hormones (control culture), progesterone production by the granulosa cells in response to FSH is significantly reduced (2.9 pg/micrograms cell protein). Cells cultured with prostaglandin E2 (PGE2, 1 microgram/ml) or dibutyryl-cAMP (dbcAMP, 1 mM) exhibited a discernibly greater steroidogenic response to FSH (12.5 and 53.4 pg/microgram cell protein, respectively) than that of control cultures. Therefore the presence of PGE2 or dbcAMP in the culture medium helps to maintain the steroidogenic capacity of granulosa cells in culture. It is probable that this capacity is maintained at a locus distal to the production of cAMP by FSH. Paradoxically, granulosa cells cultured with PGE2 produce less cAMP in response to FSH stimulation than cells in control cultures (15.9 vs. 250.3 fm/micrograms cell protein). This may be due to a suppressive effect of prior exposure to PGE2 on the subsequent activity of adenylate cyclase when the FSH is introduced and a concomitant elevation of phosphodiesterase activity.

Estradiol-17 beta and androgen secretion by isolated porcine ovarian follicular cells in vitro

The cellular sources and gonadotropic regulation of porcine ovarian estrogen and androgen were assessed by culturing isolated granulosa cells and thecal cells from medium size follicles (4-6 mm diameter) separately for 24 h in a chemically defined medium containing gonadotropins and (or) testosterone. At the end of the culture period, estradiol-17 beta (estradiol) and androgens in the media were determined by radioimmunoassays. Production of estradiol by granulosa cells without an exogenous aromatizable androgen was low in the absence or presence of a highly purified preparation of either follicle-stimulating hormone (FSH. 0.25 microgram/mL) or luteinizing hormone (LH. 1 microgram/mL). Addition of testosterone or androstenedione (0.5 microM), but not dihydrotestosterone or pregnenolone, significantly increased estradiol secretion. Additional increases were observed when FSH, LH, prostaglandin E2, or dibutyryl cyclic 3'.5'-adenosine monophosphate was present. Production of estradiol by thecal cells was low in the presence or absence of exogenous testosterone, and was essentially unaffected by the presence of gonadotropins. Thecal cells, however, released large amounts of androstenedione and smaller amounts of testosterone and other androgens during 24-h culture and the production of these androgens was stimulated by LH but not by FSH. Androgen secretion by granulosa cells was negligible when compared with the theca and was unaffected by gonadotropins. It is concluded that the theca is the prime site for follicular androgen biosynthesis by the porcine ovarian follicle, and, upon LH stimulation, may provide androgen precursors for estradiol production by granulosa cells.