Biomedical subjects

D T Armstrong

Publications and source records attributed to D T Armstrong.

At least 91 records · Page 5Linked to original sources

PubMed1990

Morphologic changes in the rat uterus following natural mating and embryo transfer.

In order to gain some insight into the putative immune suppression that may be induced at the placental implantation sites, the morphological changes at these sites following natural matings and following the transfer of embryos fertilized in vivo were studied. The only histologic parameter that showed a significant difference was the number of granulated metrial gland (GMG) cells. More GMG cells were present in allogeneic than in syngeneic pregnancies, and more GMG cells were present following embryo transfer into an allogeneic female than following the comparable natural mating. The role of the GMG cells in pregnancy is, however, still unresolved.

Animals↗

PubMed1989

Induction of hemopoietic chimerism in the caprine fetus by intraperitoneal injection of fetal liver cells.

Intraperitoneal injection of allogeneic liver cells from 43-day-old male fetuses into normal 60-day female goat fetuses resulted in persistent hemopoietic chimerism in surviving recipients without clinical evidence of graft-versus-host disease. Transplantation of normal fetal liver cells into preimmunocompetent goat fetuses affected with beta-D-mannosidosis may provide an alternative strategy for evaluating hemopoietic stem cell transplantation in the treatment of human lysosomal storage diseases.

Animals↗

PubMed1989

Preimplantation embryo development and serum steroid levels in immature rats induced to ovulate or superovulate with pregnant mares' serum gonadotropin injection or follicle-stimulating hormone infusions.

Follicular stimulation protocols using pregnant mares' serum gonadotropin (PMSG) or a follicle-stimulating hormone (FSH) preparation were compared to evaluate the yield and quality of embryos obtained from immature rats. Rats received a superovulatory dose of PMSG (40 IU), a nonsuperovulatory dose of the same gonadotrophin (4 IU), or a continuous s.c. infusion over a 72-h period with a purified FSH preparation containing an optimum ratio of luteinizing hormone (LH): FSH (FSH-hCG). The females were caged with fertile males on the evening of the 3rd day of gonadotropin treatment and scored for the occurrence of mating on the next morning; subgroups were killed on days 1-4 of pregnancy. High fertilization rates were observed in rats treated with 4 IU PMSG (84.1%) and in rats infused with FSH-hCG (91.0%); however, a much lower fertilization rate was observed following treatment with 40 IU PMSG (41.5%). From median ovulation rates of 9 and 79 in rats treated with 4 IU PMSG and in rats infused with FSH-hCG, medians of 8 and 69 embryos, respectively, were recovered from reproductive tracts flushed on day 4 of pregnancy, from which 75% were morulae or blastocysts; in contrast, from a median ovulation rate of 42.5, a median of only 12 embryos was recovered on day 3 of pregnancy following superovulation with 40 IU PMSG of which 80% were degenerate ova. Serum steroid profiles during the first 4 days of pregnancy differed significantly among treatment groups, the major differences being in substantially elevated levels of estradiol and androgens on days 1-3 in rats receiving the high (40 IU) dose of PMSG. Levels of these steroids in rats superovulated with the FSH-hCG infusion regimen were only marginally elevated above levels observed in rats treated with the low (4 IU) nonsuperovulatory dose of PMSG. Consistent with high ovulation rates, serum progesterone levels rose to considerably higher levels during the period in both superovulated groups than in animals receiving the low, nonsuperovulatory dose of PMSG. This work describes a novel method to superovulate rats (FSH-hCG) leading to high yields of normally developing embryos at all preimplantation stages and illustrates the close association between high yield of embryos and low levels of circulating androgens and estradiol-17 beta during the preimplantation period.

Animals↗

PubMed1989

Effects of follicle-stimulating hormone and ovarian steroids during in vitro meiotic maturation on fertilization of rat oocytes.

The present study examined the effects of gonadotropins and ovarian steroids during in vitro meiotic maturation of rat oocytes on their ability to undergo in vitro fertilization. Fully grown oocytes were isolated from antral follicles of immature rats and cultured as oocyte-cumulus cell complexes (OCC) under conditions in which completion of meiotic maturation occurs spontaneously. They were then exposed to spermatozoa under conditions in which oocytes matured in vivo exhibit high fertilization rates. Compared with oocytes from pregnant mare's serum gonadotropin (PMSG) or follicle-stimulating hormone (FSH)-treated rats, a similar proportion of the oocytes (greater than 80%) from untreated rats underwent germinal vesicle breakdown, but such oocytes had a lower rate of fertilization (70% vs. 20%). The presence of FSH during in vitro maturation restored the fertilization rate for oocytes from untreated rats, while a cytochrome P450 inhibitor, aminoglutethimide phosphate abolished this beneficial effect of FSH. The addition of progesterone during the in vitro maturation period duplicated the beneficial effect of FSH on fertilization rate of oocytes from untreated rats; oestradiol-17 beta was less effective in this regard, and 5 alpha-dihydrotestosterone was ineffective. These findings indicate that FSH and progesterone, although having no apparent effect on nuclear maturation of the oocyte, play an important role during oocyte maturation in enabling normal fertilization to occur.

Animals↗

PubMed1989

Growth and development of rat oocytes in vitro.

Rat oocytes from preantral follicles have been shown to grow and acquire meiotic competence in vitro. Follicles were isolated by enzymatic digestion of ovaries from infant (10- or 11-day-old) Wistar rats. Follicles were cultured for up to 20 days in Minimum Essential Medium (MEM) supplemented with 2 mM hypoxanthine to maintain meiotic arrest. When cultures were begun, oocytes were in midgrowth phase (40-45 microns diameter), and were incapable of undergoing meiotic maturation when placed in hypoxanthine-free MEM. Oocytes grew and acquired meiotic competence during culture for 20 days attaining mean diameters of 62.6 +/- 0.6 microns and 61.1 +/- 0.6 microns in two experiments. Germinal vesicle breakdown (GVB) occurred in 60-70% of oocytes when transferred to MEM without hypoxanthine. Concomitant with oocyte growth and maturation were spontaneous increases in follicular production of progestins, androgens and estrogens. When oocytes grown and matured in this system were inseminated in vitro with epididymal sperm, 36.1% and 25.8% were penetrated by one or more sperm in two experiments. However, fertilization was not generally normal with multiple penetrations and abnormal numbers of pronuclei (one or three) being common, suggesting that in these oocytes cytoplasmic maturation was incomplete or abnormal. In the two experiments, normal fertilization (two pronuclei and one sperm tail in the vitellus) occurred in 34.6% and 47.1% of penetrated oocytes with development of these apparently normal zygotes to two-cell embryos being 66.7% and 62.5%, respectively.

20-alpha-Dihydroprogesterone↗

PubMed1989

Lack of correlation of immunosuppressive activity secreted by human in vitro fertilized (IVF) ova with successful pregnancy.

The high rate of implantation failure in humans following in vitro fertilization (IVF) has been attributed to a lack of production of immunosuppressive factors by cleaved embryos, rendering them vulnerable to maternal immune attack just before or around implantation. Systemic as well as blastocyst-secreted suppressor factors have been described and claimed to be responsible for successful pregnancy. Experimentally, we have screened in a double-blind fashion the suppressive activity of human embryo culture media (B2 Menezo system, France) in which zygotes after decoronization were individually cultured during 24 hr on lymphocyte proliferation as well as natural killer (NK) activity. Suppressive activity in media from cleaved and uncleaved ova did not differ significantly, and activity in media from transferred embryos was not correlated significantly with successful pregnancy. The implications of these data are discussed.

Analysis of Variance↗

PubMed1989

Effects of lymphokines and immune complexes on murine placental cell growth in vitro.

Isolated murine placental cells obtained at Day 16 of allogeneic gestation (C3H x DBA/2J) were cultured for 3 days alone or in coculture with irradiated mouse splenocytes at the end of which 3H-thymidine was added for an additional 18-h culture to assess cell proliferation. Placental cell proliferation was significantly enhanced at spleen cell:placental cell ratios of 10:1 and 25:1 above that observed in the absence of added spleen cells. The stimulatory effect of irradiated allogeneic (C3H plus Balb/cJ) spleen cell cultures was significantly greater (approximately 2-fold) than that of isogeneic spleen cells (C3H alone). Conditioned medium from murine spleen cells cultured with concanavalin A (ConA) to induce lymphokine production had dose-dependent inhibitory effects on proliferation when added to placental cell cultures over a range of concentrations from 10 to 40% (vol:vol). Addition of pseudo "immune complexes" in the form of heat-aggregated human gamma globulin (AHGG) to culture medium failed to alter placental cell proliferation over a range of concentrations from 2 to 200 micrograms/ml either in the absence or presence of ConA-conditioned medium. In contrast to late-gestational stage placental cells, cell suspensions obtained from Days 8-9 murine ectoplacental cone (EPC) outgrowths, or from earlier stage placentas (Days 12-14) responded to low concentrations of conditioned medium from ConA-stimulated splenocytes with increased proliferation. The effect was less impressive on placental cells at gestational ages later than 12 days than on earlier stage preparations. On all placental cell suspensions tested, as well as EPC cells, a clear-cut inhibition of growth was observed at high doses of conditioned medium.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗

PubMed1989

Role of cumulus cells and serum on the in vitro maturation, fertilization, and subsequent development of rat oocytes.

Immature oocytes were collected from immature female rats (60-65 g) 40 h after injection with 6 IU pregnant mare's serum gonadotropin (PMSG). Oocytes were matured cumulus-intact (CI) or cumulus-free (CF) in medium supplemented with 0.5% bovine serum albumin (BSA) or 5-20% serum for periods of up to 24 h. After assessment for nuclear maturation, the oocytes were exposed to epididymal sperm for fertilization in vitro. In vitro-matured and ovulated oocytes undergoing fertilization were transferred to unilaterally pregnant recipients for embryonic and fetal development. The presence of cumulus cells and serum shortened (by 2 h) the time required for polar body emission by in vitro-matured oocytes and also helped to increase significantly the penetrability of the oocytes by spermatozoa. A high proportion (45.6%) of fertilized oocytes showed evidence of abnormal fertilization following maturation in the absence of cumulus cells. Oocytes matured CI before fertilization were able to develop to viable fetuses (57.8%) in proportions similar to ovulated oocytes (55.0%) after in vitro fertilization. These findings indicate an essential role for cumulus cells in promoting normal cytoplasmic maturation of oocytes necessary for pronuclear formation and subsequent developmental capability.

Animals↗

PubMed1989

Insulin enhances luteinizing hormone-stimulated steroidogenesis by porcine theca cells.

It has been shown recently that insulin enhances differentiation of rat, pig, and human granulosa cells. The present studies were done to determine if insulin also plays a role in the regulation of theca cell steroidogenesis. Theca cells were obtained from prepubertal gilts and cultured under serum-free conditions for 48 h. Theca cell androstenedione production under basal and luteinizing hormone (LH)-stimulated conditions was significantly increased by adding insulin (1 microgram/ml) to the culture medium. Treatment of basal and LH-stimulated cultures with increasing concentrations of insulin (0.001-10 micrograms/ml) caused dose- and time-dependent increments in androstenedione production, but the effect was independent of the dose of LH employed. The ability of insulin to enhance thecal cell androstenedione production was mimicked by somatomedin C, but not by relaxin. Studies to determine the mechanism(s) of action of insulin showed that insulin action is exerted, at least in part, at a site(s) proximal to cyclic adenosine 3'5'-monophosphate (cAMP) generation, since insulin enhanced both basal and LH-stimulated accumulation of extracellular cAMP in addition to increasing androstenedione production. This effect was further enhanced by 3-isobutyl-1-methyl xanthine, an inhibitor of phosphodiesterase activity. Insulin treatment also caused dose-dependent increments in forskolin- and prostaglandin E2-stimulated accumulation of extracellular cAMP and androstenedione. Insulin also increased both the basal and LH-stimulated production of progesterone and its precursor pregnenolone, in addition to the increases in androstenedione.(ABSTRACT TRUNCATED AT 250 WORDS)

1-Methyl-3-isobutylxanthine↗

PubMed1989

Zona drilling increases the penetrability of rat oocytes matured in vitro.

Immature rat follicular oocytes were cultured either with cumulus cells intact (CI) or cumulus-free (CF) in bovine serum albumin (BSA)- or serum-supplemented medium under conditions in which meiotic maturation occurs spontaneously. After 12 h of culture to permit in vitro maturation (IVM), the cumulus cells were stripped from the CI group. Control oocytes recovered 2-4 h after ovulation from oviducts of pregnant mare's serum gonadotropin (PMSG)-treated rats were similarly stripped of cumulus cells. Half the oocytes in each group had holes "drilled" in their zonae pellucidae by topical application of acid Tyrode's solution with a micropipette to enable bypass of the zona barrier to penetration. They were cultured for a further 14-16 h with epididymal sperm and then were assessed for sperm penetration and pronuclear formation. In a preliminary study using various concentration of sperm, 50,000 sperm/ml was identified as an appropriate concentration and was used in all subsequent experiments. For oocytes matured in serum-supplemented medium, penetration rates of non-drilled oocytes-expressed as a percentage of oocytes exposed to sperm for CF, CI, and ovulated oocytes were 10%, 34%, and 80%, respectively (p less than 0.01). Drilling significantly increased the penetration rates of both IVM groups (CF: 40%, CI: 77%) but not of ovulated oocytes (78%). Forty-one percent of non-drilled CF oocytes failed to form normal pronuclei after penetration. This was significantly higher than either the CI (0%) or ovulated (1%) groups (p less than 0.001). Drilling increased the incidence of failure to form normal pronuclei in penetrated oocytes of the CF group (64%) but not of the CI or ovulated groups.2z=

Animals↗

PubMed1989

Effects of luteinizing hormone on superovulatory and steroidogenic responses of rat ovaries to infusion with follicle-stimulating hormone.

Immature female rats were infused s.c. continuously over a 60-h period with a partially purified porcine pituitary follicle-stimulating hormone (FSH) preparation having FSH activity 4.2 x NIH-FSH-S1 and luteinizing hormone (LH) activity 0.022 x NIH-LH-S1. High rates of superovulation were observed in rats receiving 1 U FSH/day, with 69 +/- 11 oocytes/rat recovered as cumulus-enclosed oocytes from oviducts on Day 1 (equivalent to the day of estrus). Addition of LH to the FSH, at dosages equivalent to 2.5-100 micrograms/day NIH-LH-S1 equivalents (2.5-100 mU) resulted in a dose-related inhibition of superovulation, reaching a nadir of 15 +/- 7 oocytes recovered from rats receiving 50 mU LH/day together with 1 U FSH/day. At the two highest LH doses, 50 and 100 mU/day, ovulation was advanced so that 12 +/- 3 and 15 +/- 4 oocytes, respectively, were recovered from oviducts of these rats flushed on the morning of Day 0, compared to none in rats infused with FSH alone. Ovarian steroid concentrations (ng/mg) observed on the morning of Day 0 in rats infused with FSH alone were progesterone, 0.50 +/- 0.13; testosterone, 0.16 +/- 0.08; androstenedione, 0.06; and estradiol, 0.23 +/- 0.05. On the morning of Day 1, ovarian progesterone concentrations in rats infused with FSH alone had risen to 3.30 +/- 0.33 ng/mg, whereas concentrations of testosterone, androstenedione, and estradiol, had fallen to essentially undetectable levels. Addition of LH to the FSH infusion resulted in dose-related increases, on Day 0, of all four steroids up to a dosage of 25 mU LH/day. At higher LH dosages, Day 0 ovarian concentrations of androgens and estradiol fell markedly, while progesterone concentrations continued to increase. Histological examination of ovaries revealed increases in the extent of luteinization of granulosa cells in follicles with retained oocytes on both Days 0 and 1 in rats infused with 25 and 50 mU LH/day together with 1 U FSH/day, compared to those observed in rats receiving FSH alone. These findings indicate that the elevated progesterone levels on Day 0 and inhibition of ovulation observed at these LH doses were due to premature luteinization of follicles, thus preventing ovulation. At lower LH doses, no sign (based on histologic or steroidogenic criteria) of premature luteinization was evident, suggesting that the decreased superovulation in these rats was due to decreased follicular maturation and/or increased atresia rather than to luteinization of follicles without ovulation.(ABSTRACT TRUNCATED AT 400 WORDS)

Animals↗

PubMed1989

Bimodal effects of luteinizing hormone and role of androgens in modifying superovulatory responses of rats to infusion with purified porcine follicle-stimulating hormone.

Prepubertal (28-30 days old) female rats were infused s.c. over a 60-h period with a purified porcine pituitary follicle-stimulating hormone (FSH) preparation having FSH specific activity 8.4 times that of NIH-FSH-S1 and luteinizing hormone (LH) specific activity less than 0.005 times that of NIH-LH-S1, based on radioreceptor assays. When the FSH infusion rate of this preparation was increased over the range of 0.5-2 units/day (mg NIH-FSH-S1 equivalent), an all-or-none response was observed, with the threshold dose for superovulation being between 1 and 2 units/day. Eleven of twelve rats receiving the 2 units/day dose ovulated a mean +/- SEM of 67 +/- 8 oocytes on the morning of the third day after the beginning of FSH infusion. Addition of human chorionic gonadotrophin (hCG), as a source of LH activity, to a subthreshold (1 U/day) FSH infusion rate resulted in 20% of rats ovulating at an hCG dosage of 50 mIU/day; increasing the hCG infusion to 200 mIU/day concomitant with the subthreshold FSH infusion rate increased ovulation rate to a mean of 69 +/- 8/rat, with 100% of rats ovulating. To determine the effect of varying both FSH infusion rates and LH:FSH ratios, FSH was infused at several rates, with hCG added to give varying hCG:FSH ratios for each FSH infusion rate. Administration of hCG alone was ineffective in causing ovulation except at the highest infusion rates. Adding hCG to FSH to reach a ratio of 0.2 IU hCG/U FSH significantly increased the superovulatory response to an intermediate, 1 U/day FSH dose, but not to the low, 0.5 U/day dose.(ABSTRACT TRUNCATED AT 250 WORDS)

Androgens↗

PubMed1989

Catecholestrogens inhibit basal and luteinizing hormone-stimulated androgen production by porcine thecal cells.

It has been shown recently that catecholestrogens are produced by cultured porcine granulosa and thecal cells, and that they influence porcine granulosa cell steroidogenesis in a similar manner to estradiol-17 beta (E2). The present studies were performed to determine if catecholestrogens also play a role in the regulation of porcine thecal cell steroidogenesis and to compare their actions to those of E2. Thecal cells were obtained from prepubertal gilts and cultured in a serum-free medium for 48 h. Thecal cell androstenedione production under basal and luteinizing hormone (LH)-stimulated conditions was significantly inhibited by adding E2 or catecholestrogens to the culture medium. Treatment of basal and LH-stimulated cultures with increasing concentrations of E2 or catecholestrogens (0.1-10 micrograms/ml) caused a dose-and time-dependent inhibition of androstenedione production. The inhibitory effect of the catecholestrogens, but not of E2, was enhanced when the cultures contained the catechol-O-methyl transferase inhibitor, U-0521. Studies to determine the mechanism(s) of action of the catecholestrogens showed that E2 and catecholestrogen actions are exerted at a site(s) distal to cyclic adenosine 3'5' monophosphate (cyclic AMP) generation, because neither agent affected the basal or LH-stimulated accumulation of extracellular cyclic AMP, while causing a significant inhibition of androstenedione production. E2 or catecholestrogen treatment also inhibited androstenedione production stimulated by prostaglandin E2 and dibutyryl cyclic AMP. In addition, both E2 and catecholestrogen treatment significantly decreased basal and LH-stimulated 17 alpha-hydroxyprogesterone production, while significantly increasing pregnenolone production. Progesterone production in the presence of E2 or catecholestrogens showed small but statistically insignificant increases.(ABSTRACT TRUNCATED AT 250 WORDS)

17-alpha-Hydroxyprogesterone↗

PubMed1989

Ovarian nerve extracts influence androgen production by cultured ovarian thecal cells.

There is growing evidence that ovarian steroidogenesis is controlled not only by pituitary gonadotropins but also by ovarian nerves. Nerves reach the ovary via the plexus nerve and via the superior ovarian nerve (SON), which runs in the suspensory ligament, and innervate theca cells of all sizes of follicles. To investigate the role of ovarian nerves in steroidogenesis we have examined the effects of adding an extract of SON from adult rats on androgen production by cultured porcine theca cells. Addition of SON extract to cultured theca interna from 3 to 6 mm diameter follicles of prepubertal gilts significantly inhibited (p less than 0.05) LH-stimulated androstenedione production in a dose-dependent manner; significant inhibition (10.8%) occurred with the addition of the extract of 2 mg of SON/ml culture medium, and near maximal inhibition (83%) resulted when the SON extract was increased to 60 mg SON/ml. Extracts of sciatic nerves, used as non-ovarian nerve controls, failed to inhibit, and in fact significantly increased (p less than 0.05) androstenedione production over the same concentration range of neural tissue extract. The inhibitory effect of the SON extract was unaffected by chymotrypsin digestion or by the presence of the beta-adrenergic antagonist propranolol (10(-6) M), but was removed by charcoal treatment. These results suggest that the nervous system has the potential for modulation of follicular steroid biosynthesis via direct innervation of the ovaries, in addition to the well-established indirect mechanism of neural control exerted via the hypothalamic-pituitary system.

Adipose Tissue↗

PubMed1989

Mevinolin (lovastatin) inhibits androstenedione production by porcine ovarian theca cells at the level of the 17 alpha-hydroxylase:C-17,20-lyase complex.

Mevinolin, putatively a specific inhibitor of 3-hydroxy-3-methylglutaryl coenzyme-A reductase, was used to assess the contribution of de novo synthesized cholesterol to androgen production by ovarian thecal cells in vitro. Enzymatically dispersed thecal cells from 3- to 6-mm follicles of prepubertal gilts were incubated at 150,000 cells/ml with a maximally effective dose of LH (250 ng/ml) for 24 h. Mevinolin (3-50 microM) caused dose-dependent inhibition of androstenedione production. Addition of 25-hydroxycholesterol (0.025-25 microM) failed to restore androstenedione production to levels seen in the absence of mevinolin, suggesting an additional site of action of mevinolin beyond 3-hydroxy-3-methylglutaryl coenzyme reductase. The site of this inhibitory effect was determined by measuring steroid products formed in the presence of relevant steroid precursors. Mevinolin (12 microM) inhibited the production of 17 alpha-hydroxyprogesterone from progesterone and that of androstenedione from 17 alpha-hydroxyprogesterone, while 25-hydroxycholesterol to progesterone and pregnenolone to progesterone conversions were unimpaired. That mevinolin did not affect 3 beta-hydroxysteroid dehydrogenase:delta 5-delta 4-isomerase reactions was confirmed by demonstrating that conversions of pregnenolone, 17 alpha-hydroxypregnenolone, and dehydroepiandrosterone to progesterone, 17 alpha-hydroxyprogesterone, and androstenedione, respectively, were not affected by 12 microM mevinolin. These results indicate that mevinolin has an additional inhibitory action at the level of the 17 alpha-hydroxylase:C-17,20-lyase complex. The degree of inhibition of androstenedione production was not decreased with increased concentrations of progesterone or 17 alpha-hydroxyprogesterone substrate, suggesting that the inhibition was not competitive in nature. As the dose of mevinolin was increased up to 50 microM, progesterone accumulation was unaffected, but pregnenolone concentrations in medium greatly increased. While the mechanism of this effect is unclear, this finding suggests that preformed intracellular cholesterol, rather than that synthesized de novo, is supplying steroidogenic substrate in these cells.

Aldehyde-Lyases↗

PubMed1989

Ability of progesterone to reverse anti-androgen (hydroxyflutamide)-induced interference with the preovulatory LH surge and ovulation in PMSG-primed immature rats.

In Exp. 1, PMSG was injected to 26-day-old prepubertal rats to induce ovulations. On Day 2 (2 days later, the equivalent of the day of pro-oestrus) they received at 08:00 h 5 mg hydroxyflutamide or vehicle and at 12:00 h 2 mg progesterone or testosterone or vehicle. Animals were killed at 18:00 h on Day 2 or at 09:00 h on Day 3. Progesterone but not testosterone restored the preovulatory LH surge and ovulation in hydroxyflutamide-treated rats. In Exp. 2, 2 mg progesterone or testosterone were injected between 10:30 and 11:00 h on Day 2, to advance the pro-oestrous LH surge and ovulation in PMSG-primed prepubertal rats. Injection of hydroxyflutamide abolished the ability of progesterone to advance the LH surge or ovulation. Testosterone did not induce the advancement of LH surge or ovulation. In Exp. 3, ovariectomized prepubertal rats implanted with oestradiol-17 beta showed significantly (P less than 0.01) elevated serum LH concentrations at 18:00 h over those observed at 10:00 h. Progesterone injection to these animals further elevated the serum LH concentrations at 18:00 h, in a dose-dependent manner, with maximal values resulting from 1 mg progesterone. Hydroxyflutamide treatment significantly (P less than 0.003) reduced the serum LH values in rats receiving 0-1 mg progesterone but 2 mg progesterone were able to overcome this inhibition. It is concluded that progesterone but not testosterone can reverse the effects of hydroxyflutamide on the preovulatory LH surge and ovulation. It appears that hydroxyflutamide may interfere with progesterone action in induction of the LH surge, suggesting a hitherto undescribed anti-progestagenic action of hydroxyflutamide.

Anilides↗

PubMed1989

Preovulatory biosynthesis and granulosa cell secretion of immunoreactive oxytocin by goat ovaries.

Oestrous cycles of goats were synchronized hormonally. Immunoreactive oxytocin was undetectable (less than 0.1 ng/mg protein) in media from granulosa cells isolated before the LH surge for small (1-2 mm), medium (3-5 mm) and large (greater than 5 mm diameter) follicles when cultured for 24 h without or with added hormones. Granulosa cells from large and medium, but not small, follicles isolated 6-12 h after spontaneous preovulatory LH surges secreted high concentrations of oxytocin (4-12 ng/mg protein). Addition of PGE-2 (1 microgram/ml) caused a further significant (P less than 0.05) increase in oxytocin secretion by cultured granulosa cells, whereas PGF-2 alpha, FSH and LH were ineffective when added to culture media. Ovarian venous blood and granulosa cells were collected at 0, 6, 12 or 18 h after GnRH injection in hormonally synchronized goats. Peripheral serum LH values were increased significantly in all but 2 of 22 goats within 2 h of GnRH injection. At the earliest sampling time after GnRH (6 h), ovarian venous levels of oxytocin were increased significantly from basal levels of 0.4 pg/ml to 2.4 pg/ml. Oxytocin concentrations in follicular fluid increased from a basal value of 67 pg/ml to 155 pg/ml by 6 h and to 372 pg/ml by 18 h after GnRH injection. Oxytocin secretion by cultured granulosa cells was not increased significantly by 6 h (0.1 ng/mg protein) but rose to 1.4 and 3.5 ng/mg protein at 12 and 18 h, respectively. Approximately parallel increases occurred in progesterone in ovarian venous blood and granulosa cell culture media over the same time period. (ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗

PubMed1989

Formation of 4-oestrene-3,17-dione (19-norandrostenedione) by porcine granulosa cells in vitro is inhibited by the aromatase inhibitor 4-hydroxyandrostenedione and the cytochrome P-450 inhibitors aminoglutethimide phosphate and ketoconazole.

The origin and biosynthesis of 4-oestrene-3,17-dione (19-norandrostenedione), a major steroid in porcine ovarian follicular fluid, was investigated by culturing granulosa cells from 4-6 mm follicles of prepubertal gilts with radiolabelled androstenedione and 19-hydroxyandrostenedione. Steroid metabolites were purified by solvent extraction and lipophilic column chromatography, and analysed by C18 reverse-phase high-performance liquid chromatography. 19-Hydroxyandrostenedione, 19-norandrostenedione and oestradiol-17 beta were obtained as major metabolites from androstenedione, while 19-norandrostenedione and oestradiol-17 beta were the major products from 19-hydroxyandrostenedione. Serum alone or serum plus FSH significantly enhanced formation of 19-norandrostenedione and oestradiol-17 beta from each substrate, compared with controls. Micromolar concentrations (1 mumol/l) of 4-hydroxyandrostenedione, an aromatase inhibitor, significantly reduced formation of 19-norandrostenedione and oestradiol-17 beta by granulosa cells cultured with serum and FSH. Formation of 19-norandrostenedione and oestradiol-17 beta from androstenedione and 19-hydroxyandrostenedione was also significantly inhibited by aminoglutethimide phosphate, a cytochrome P-450 inhibitor known to block the conversion of androstenedione to oestrogens. Ketoconazole, an inhibitor of the cytochrome P-450 dependent 17,20-lysase, blocked formation of 19-norandrostenedione and oestradiol-17 beta only at millimolar concentrations. These results suggest that 19-norsteroid and oestrogen formation from C19 aromatizable androgens may share a common or overlapping pathway, and imply that 19-norsteroid and oestrogen synthesis is mediated by cytochrome P-450 dependent enzymes.

Aminoglutethimide↗