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Biomedical subjects

G F Erickson

Publications and source records attributed to G F Erickson.

At least 73 records · Page 4Linked to original sources
PubMed1983

Epidermal growth factor antagonizes ovarian theca-interstitial cytodifferentiation.

This study was aimed at testing the hypothesis that epidermal growth factor (EGF) can modulate the gonadotropin-dependent differentiation of theca-interstitial cells in vitro. Addition of EGF to chemically defined culture medium severely antagonized the ability of hCG to transform undifferentiated theca-interstitial cells into active androgen-producing cells. The inhibitory action of EGF was dose-dependent, hormone-specific, and independent of granulosa cells. Since ovarian androgens are obligatory precursors to estrogen formation and induce atresia, a repressive action of EGF on theca-interstitial cytodifferentiation has new implications for understanding the way in which follicles develop in the ovary.

Androgens↗
PubMed1983

Role of serum-free defined medium in regulation of LH receptor in cultured rat granulosa cells.

The induction of luteinizing hormone (LH) receptor by follicle-stimulating hormone (FSH) in granulosa cells was compared following culture in serum-free or serum-containing medium. Incubation of primary cultures of granulosa cells in serum-free defined medium with purified FSH resulted in dramatic increases in the level of functional LH receptors. This striking enhancement of LH receptor by FSH was completely abolished by concomitant incubation with serum (rat, horse, porcine, human or calf). The serum inhibition of FSH was not readily reversible and could be evoked throughout the culture period. The synthesis of cAMP by FSH was markedly suppressed by serum, suggesting that serum component(s) are inhibiting FSH action at the level of adenylate cyclase. Such an action, however, cannot be the sole mechanism because serum also blocked LH receptor induction by cyclic AMP analogs. In defined medium, addition of insulin, transferrin, dexamethasone or fibronectin alone had no effect on basal levels of LH receptor. However, following incubation with either insulin or dexamethasone, the FSH-induced increases in LH receptor were markedly suppressed. Insulin was found to markedly inhibit FSH-stimulated cyclic AMP formation; this was not the case with dexamethasone. The present results demonstrated the complete inhibition of FSH action by serum in cultured granulosa cells and suggest that the effect is caused by a combination of direct actions of common metabolic hormones which inhibit FSH action at multiple sites. These experiments clearly indicate the obligatory role of defined medium in the hormone-dependent differentiation of the granulosa cell in culture.

Adenylyl Cyclases↗
PubMed1982

Rat ovary glucocorticoid receptor: identification and characterization.

A soluble, thermolabile protein with characteristics typical of glucocorticoid receptors has been identified in the ovaries of estrogen-stimulated hypophysectomized immature rats. After the incubation of 3H- dexamethasone with ovarian cytosol, fractionation on a Sephadex G-200 column reveals a peak of radioactivity which elutes at the void volume. This peak, which represents saturable 3H-dexamethasone binding, disappears following heating (4 degrees C X 15 min) or treatment of the cytosol with pronase. Scatchard analysis of the 3H-dexamethasone binding to cytosol shows it to be high affinity (Kd=5.1 nM) and saturable, with 327 fmol binding sites/mg cytosol protein. Binding site number rises linearly with increasing cytosol protein concentrations. The relative abilities of various steroids to inhibit 3H-dexamethasone binding are: triamcinolone acetonide greater than or equal to dexamethasone greater than cortisol = progesterone greater than dihydro-testosterone greater than estradiol. This binding protein sediments at 9 S on a sucrose gradient, has a mean Stokes radius of 105 A on gel exclusion chromatography, and has a calculated molecular weight of 388,000 daltons and a frictional ratio of 2.1. 3H-Dexamethasone is not metabolized and does not bind specifically to serum. We have identified a protein in the rat ovary with characteristics of a glucocorticoid receptor and propose that this protein may be responsible for mediating direct effects of glucocorticoids on the ovary.

Animals↗
PubMed1982

Direct inhibitory effect of estrogen on LH-stimulated androgen synthesis by ovarian cells cultured in defined medium.

The direct inhibitory effect of estrogen on ovarian androgen synthesis was investigated. When primary cultures of rat ovarian theca-interstitial cells were grown in defined medium with LH there was a marked increase in androgen synthesis of which 98% was androsterone (control = 11 +/- 2 ng; LH = 1219 +/- 217 ng/ml/10(6) cells). Diethylstilbestrol (DES), estrone (E1), estradiol (E2), and estriol (E3) inhibited LH-stimulated androsterone synthesis by 81%, 81%, 81%, and 47%, respectively. The ED50's of the estrogens were: DES = 4.2 +/- 2.1 X 10(-9) M; E1 = E2 = 9.5 +/- 2.4 X 10(-8) M; and E3 = 3.8 +/- 2.6 X 10(-7) M. The estrogen effect was very rapid (t1/2 = 10 min) and long-lasting. Metabolic studies revealed that estrogen inhibited androsterone, androstenedione, 5 alpha-androstane-3 alpha, 17 beta-diol, and testosterone accumulation by 80%, dehydroepiandrosterone and 17 alpha-hydroxypregnenolone by 40%, 17 alpha-hydroxyprogesterone by 30%, while pregnenolone and progesterone were unchanged. These results prove, for the first time, that estrogen can directly inhibit LH-stimulated androgen production in ovarian theca-interstitial cells and suggest that mechanism involves, at least in part, a rapid selective inhibition of the 17 alpha-hydroxylase/C17-20 desmolase activities.

Androgens↗
PubMed1982

Mechanism by which GnRH inhibits androgen synthesis directly in ovarian interstitial cells.

The mechanism by which GnRH acts on ovarian interstitial cells to inhibit androgen synthesis was studied in primary cultures of ovarian cells from hypophysectomized immature rats. Interstitial cells cultured in defined medium with LH showed a 200-fold increase in steroid production, of which androsterone was the principal metabolite (88% of the total steroid content). Treatment with GnRH (10(-8) M) inhibited LH-stimulated androsterone production by 92%. This inhibitory effect of GnRH was not due to changes in cell number, cell viability, or 125-I-hCG binding capacity. Prostaglandin E2, cholera toxin and 8-Br-cyclic AMP mimicked the LH effect on androsterone synthesis and these increases were also inhibited by GnRH. Metabolic studies of GnRH-treated cultures revealed that LH-stimulated androsterone and 5 alpha-androstane-3 alpha, 17 beta-diol were decreased by 90%; androstenedione, testosterone and DHEA were decreased by 70%; 17 alpha-hydroxypregnenolone and 17 alpha-hydroxyprogesterone were decreased by 50%; pregnenolone was unchanged; and progesterone was increased 40%. Collectively, these results suggest that GnRH directly inhibits androgen synthesis in ovarian interstitial cells by selectively inhibiting the 17 alpha-hydroxylase and C17-20 desmolase activities.

Androgens↗
PubMed1982

The role of cyclic AMP in the induction of estrogen and progestin synthesis in cultured granulosa cells.

The role of cyclic AMP in the induction of enzymes involved in estrogen and progestin biosynthesis in undifferentiated granulosa cells was investigated. When granulosa cells from immature hypophysectomized, DES-treated rats were cultured for 2 days in serum-free medium with aromatase substrate (10(-7) M androstenedione) together with graded doses of FSH, prostaglandin E2 (PGE2), cholera toxin (CT), or dibutyryl cyclic AMP (Bu2cAmP), there was a dose-related increase in estrogen (E) production. The induction of E production by saturating doses of FSH, PGE2, CT, and Bu2cAmP required a lag phase of approximately 24 h, after which the E response increased sharply to maximum levels at day 3, and then declined gradually to day 5. Treatment for 24 h ((day 0-1) with FSH, together with 1 microgram/ml of either actinomycin D or cycloheximide, completely abolished the stimulatory action of FSH on E production. When the inhibitors were removed, the FSH-induced increases in E returned to near normal levels after a 24-h lag period. Similar effects of the inhibitors upon E production by CT, PGE2 and Bu2cAMP were observed. As with E, the production of progesterone and 20 alpha-dihydroprogesterone was markedly stimulated by FSH, PGE2, CT and Bu2cAmP, and the results of the time course, dose response, and inhibitor experiments were similar to those for E production. These results indicate that FSH induces the de novo synthesis of enzymes required for both estrogen and progestin biosynthesis by undifferentiated granulosa cells and suggest that this action is mediated by cyclic AMP.

Animals↗
PubMed1982

Progestins inhibit FSH-induced functional LH receptors in cultured rat granulosa cells.

The role of intraovarian progesterone in the control of follicular growth and development remains unclear. The presence of a rat ovary granulosa cell progesterone receptor suggests that progesterone has a direct effect on the follicles. We have previously reported that progestins inhibit FSH-stimulated estrogen production by cultured granulosa cells by inhibiting the FSH induction of the aromatase enzyme. We now report that progestins can inhibit another FSH action on rat granulosa cells; the induction of LH/hCG receptors. The concomitant administration of 10(-5) M R5020, a potent synthetic progestin, with 10 ng/ml FSH during a 2-day culture period inhibits the FSH induction of LH/hCG receptors by 75 +/- 6% (mean +/- S.E.) The progestin inhibition of the induction of LH/hCG receptors is not mediated by its inhibitory action on the induction of aromatase. Scatchard analysis indicates that progestin decreases the number of LH/hCG receptors per cell but has no effect on receptor affinity. Both R5020 and progesterone have a dose-dependent inhibitory effect on the FSH induction of LH/hCG receptors, causing a 30 and 85% decrease in receptor number at concentrations of 10(-6) and 10(-5) M, respectively. The concomitant administration of R5020 with FSH also leads to a significant decrease in the ability of LH to stimulate cAMP production, indicating that progestin is inhibiting the induction of 'functional' LH/hCG receptors. R5020 (10(-5) M) also inhibits by 90% the induction of LH/hCG receptors by cholera toxin and dibutyryl cAmP, indicating that the progestin effect is at a post-cAMP site. Since the induction of LH/hCG receptors by FSH is a necessary event in follicular maturation, these results offer another mechanism by which progestins, at high concentrations, can inhibit follicular growth and development.

Animals↗
PubMed1982

The effect of luteinizing hormone-releasing factor and its agonist on cultured human granulosa cells.

The possible direct effect of luteinizing hormone-releasing factor (LRF) and a potent LRF agonist, [D-Trp6,Pro9NEt]-LRF (LRF-Ag), on basal and follicle-stimulating hormone (FSH)-stimulated estrogen and progesterone production by cultured human granulosa cells was examined. Granulosa cells, collected from healthy follicles (4 to 12 mm in diameter) in the early to midfollicular phase were grown for 2 days in serum-free medium with aromatase substrate (androstenedione; 10(-7) M) and human FSH (100 ng/ml), LRF (10(-10) to 10(-7) M) or in LRF-Ag (10(-7) M). Granulosa cells from each follicle responded to FSH stimulation by showing marked increases (2- to 20-fold) in estrogen and progesterone production. Concomitant treatment with high doses of LRF or LRF-Ag did not alter the steroidogenic effect of FSH. These results suggest that in contrast to the rat, LRF and its agonistic analog do not act directly on human granulosa cells to inhibit acute steroidogenic function.

Adult↗
PubMed1982

Hormonal basis of reproductive defects in athymic mice: reduced gonadotropins and testosterone in males.

We wished to determine if congenitally athymic nude male mice have the same reduction in circulating concentrations of gonadotropins and gonadal steroids observed in their female counterparts when compared to their normal heterozygous littermates. We therefore quantitated pituitary and circulating concentrations of gonadotropins and circulating levels of testosterone in 102 congenitally athymic mice and 101 of their heterozygous littermates ranging in age from 1 to 120 days. Although the developmental patterns observed for both circulating luteinizing hormone (LH) and follicle-stimulating hormone (FSH) were similar to those previously observed in rats and mice, the athymic mice had significantly reduced concentrations of both pituitary and serum LH and FSH in comparison to the heterozygotes. In general, the reduced secretion of gonadotropins was most marked prior to sexual maturation but persisted in adult athymic males. Circulating concentrations of testosterone were also markedly reduced in the adult athymic males. Histologically, the number of Leydig cells appeared reduced in testes from 20-day-old athymic mice. However, no differences could be detected in testes from 40-day-old animals, and spermatogenesis appeared normal. Thus, unlike athymic females, athymic male mice appear to have normal reproductive capacity despite these hormonal abnormalities.

Animals↗
PubMed1982

Prolactin inhibition of luteinizing hormone-stimulated androgen synthesis in ovarian interstitial cells cultured in defined medium: mechanism of action.

The mechanism by which PRL acts on ovarian interstitial cells to inhibit androgen synthesis was examined using primary cultures of ovarian cells from hypophysectomized immature rats grown in serum-free medium. In the presence of LH, the cultured interstitial cells showed a 200-fold increase in androgen production, of which androsterone was the principal metabolite. The addition of highly purified PRL (100 ng/ml) markedly inhibited (98%) the LH-stimulated androsterone accumulation. The ED50 of PRL action was calculated to be 1.3 +/- 0.4 ng/ml. The inhibition of androsterone production by PRL was rapid (t 1/2 = 75 min), not readily reversible, and could be evoked at any time during the culture period. The effects of PRL on LH-stimulated androgen production were not due to changes in [125I]iodo-hCG binding. LH-stimulated adenylate cyclase, cell number, or cell viability. As with LH, prostaglandin E2, cholera toxin, or 8-bromo cAMP also caused marked increases in androsterone synthesis, and these effects were blocked (98-99%) by PRL. Studies on the metabolism of steroid hormones revealed that PRL decreased LH-stimulated androsterone and 5 alpha-androstane-3 alpha, 17 beta-diol accumulation by 99%, androstenedione by 94%, testosterone by 90%, dehydroepiandrosterone by more than 80%, pregnenolone and 17 alpha-hydroxyprogesterone by 80%, 17 alpha-hydroxypregnenolone by 84%, and progesterone by 71%. Binding experiments demonstrated the presence of a single class of high affinity (Kd = 2.42 x 10(10) M), low capacity (2.37 fmol/10(6) cells) [125I]iodo-PRL-binding sites in the interstitial cells, suggesting that such receptors mediate the inhibitory action of PRL. It is inferred from these results that PRL antagonizes the stimulatory effects of LH on ovarian androgen biosynthesis by inhibiting a step distal to cAMP formation and before or at the cholesterol side-chain cleavage step.

Androgens↗
PubMed1982

Idiopathic premature ovarian failure: clinical and endocrine characteristics.

The characteristics of 26 patients with presumptive premature ovarian failure have been examined. The initial diagnosis was based on any single serum follicle-stimulating hormone (FSH) concentration of greater than 40 mIU/ml in karyotypically normal women under 35 years of age with irregular menses or amenorrhea. Clinical manifestations were heterogeneous: some failed to undergo pubertal maturation, and other developed hypergonadotropic amenorrhea following several years of regular menses. Almost 70% experienced hot flashes. Three had thyroiditis. Nine of 18 patients had hormonal evidence of functioning ovarian follicles, and 4 of 9 women had viable oocytes on biopsy. Evidence of ovulation was noted in five patients, and spontaneous pregnancy occurred in one. These data emphasize the fallacy of using elevated FSH levels to diagnose irreversible ovarian failure and indicate the possibility of ovulation and pregnancy in some affected individuals.

Adult↗
PubMed1981

Preparation, specific binding, and biological activity of a monosubstituted fluorescein derivative of prolactin.

A monosubstituted fluorescein derivative of ovine prolactin has been prepared by the reaction of fluorescein isothiocyanate with the hormone at pH 8.0. Reaction under the specified conditions results in a derivative incorporating one fluorescein moiety per molecule of prolactin as judged by coordinated UV spectroscopy and amino acid analysis. The absence of NH2-terminal threonine in the derivative indicates that the point of fluorescein attachment is the NH2-terminal amino group, whose substitution is expected to be favored at pH 8.0. The derivative was found to retain significant specific binding on both rabbit mammary and rat ventral prostate membrane preparations in competition with 125I-labeled prolactin, and to show saturable stimulation of progesterone production in primary cultures of rat granulosa cells. It is anticipated that this derivative will be useful in studies of prolactin-target cell interactions. This study shows that NH2-terminal monosubstituted derivatives of ovine prolactin are readily formed under specified conditions at pH 8.0; these conditions may be useful in the preparation of other derivatives of this type.

Animals↗
PubMed1981

Inhibitory effect of gonadotropin releasing hormone upon cultured testicular cells.

The direct inhibitory of gonadotropin-releasing hormone (GnRH) upon testicular androgen production was studied in cultured testicular cells. Enzyme-dispersed testicular cells from immature hypophysectomized rats were cultured for 6 days in a serum-free medium with or without various hormones. Culture media were changed every 2 days and media concentration of a androgens was measured by radioimmunoassay. The testis cultures from immature rats secrete predominately 5 alpha-androstane-3 alpha, 17 beta-diol (A-diol) and androsterone but negligible amounts of androstenedione, testosterone and dihydrotestosterone. Incubation of testicular cells with hCG and FSH increased A-diol and androsterone production as compared to control cultures. In contrast, treatment with GnRH or a GnRH agonist (des-Gly10, D-Leu6 (N alpha Me)Leu7, Pro9NHEt-GnRH) inhibited the gonadotropin effect in a dose-dependent manner; 10(-8) M GnRH inhibited A-diol production by approximately 20% on day 4 and 6 of culture whereas 10(-6) M GnRH inhibited A-diol production by greater than 80%. The observed effect of GnRH upon testicular cells in primary culture demonstrates that the hypothalamic peptide directly inhibits testicular steroidogenesis.

Androgens↗
PubMed1981

Progestins inhibit FSH-stimulated granulosa estrogen production at a post-cAMP site.

The purpose of this investigation is to examine the mechanism by which progestins inhibit FSH-induced estrogen (E) production by cultured rat ovary granulosa cells. We have demonstrated that the highly potent synthetic progestin, R5020, is able to inhibit the induction of granulosa cell aromatase activity by cholera toxin, prostaglandin E2, dibutyryl cAMP or oFSH. Since the induction of E synthesis by these compounds is mediated through activation of adenylate cyclase and increased cellular cAMP production, these observations indicate that the progestin inhibitory effect is a post-cAMP event. In addition, we have demonstrated that R5020 does not inhibit FSH-stimulated granulosa cell cAMP production. The involvement of the granulosa cell progesterone (P) receptor as a mediator of this post-cAMP progestin effect is suggested by the relative abilities of various progestins to both bind the P receptor and to block the induction of granulosa cell aromatase activity by dibutyryl cAMP. While the precise mechanism of progestin action remains unclear, the kinetic analysis of aromatase enzyme activity demonstrates that progestins are not acting as competitive inhibitors of granulosa cell aromatase. Since E is necessary for follicular development, our in vitro data are consistent with the hypothesis that P is a factor which can inhibit FSH-induced follicular growth and development in the rat ovary.

Animals↗