Effects of aromatizable and nonaromatizable androgen treatments on luteinizing hormone receptors and ovulation induction in immature rats

Predictors of response to ovulation induction using letrozole in women with polycystic ovary syndrome

BACKGROUND

This study aimed to evaluate the predictive value of the initial screening characteristics of women with anovulatory polycystic ovary syndrome (PCOS) who did or did not respond to 2.5 mg letrozole (LET).

METHODS

The clinical and laboratory characteristics of women with PCOS who underwent LET treatment were evaluated. Women with PCOS were stratified according to their responses to LET (2.5 mg). The potential predictors of their responses to LET were estimated using logistic regression analysis.

RESULTS

Our retrospective study included 214 eligible patients with a response to 2.5 mg LET (n = 131) or no response to 2.5 mg LET (n = 83). PCOS patients who responded to 2.5 mg LET showed better outcomes than those who did not (2.5 mg LET) for pregnancy rate, live birth rate, pregnancy rate per patient, and live birth rate per patient. Logistic regression analyses showed that late menarche (odds ratio [OR], 1.79 [95% confidence intervals (CI), 1.22-2.64], P = 0.003), and increased anti-müllerian hormone (AMH) (OR, 1.12 [95% CI, 1.02-1.23], P = 0.02), baseline luteinizing hormone (LH)/ follicle stimulating hormone (FSH) (OR, 3.73 [95% CI, 2.12-6.64], P < 0.001), and free androgen index (FAI) (OR, 1.37 [95% CI, 1.16-1.64], P < 0.001) were associated with a higher possibility of no response to 2.5 mg LET.

CONCLUSIONS

PCOS patients with an increased LH/FSH ratio, AMH, FAI, and late menarche may need an increased dosage of LET for a treatment response, which could be helpful in designing a personalized treatment strategy.

Role of androgens in normal and pathological ovarian function

Androgens mediate their actions via the androgen receptor (AR), a member of the nuclear receptor superfamily. AR-mediated androgen action is essential in male reproductive development and function; however, only in the last decade has the suspected but unproven role for AR-mediated actions in female reproduction been firmly established. Deciphering the specific roles and precise pathways by which AR-mediated actions regulate ovarian function has been hindered by confusion on how to interpret results from pharmacological studies using androgens that can be converted into oestrogens, which exert actions via the oestrogen receptors. The generation and analysis of global and cell-specific femaleArknockout mouse models have deduced a role for AR-mediated actions in regulating ovarian function, maintaining female fertility, and have begun to unravel the mechanisms by which AR-mediated androgen actions regulate follicle health, development and ovulation. Furthermore, observational findings from human studies and animal models provide substantial evidence to support a role for AR-mediated effects not only in normal ovarian function but also in the development of the frequent ovarian pathological disorder, polycystic ovarian syndrome (PCOS). This review focuses on combining the findings from observational studies in humans, pharmacological studies and animal models to reveal the roles of AR-mediated actions in normal and pathological ovarian function. Together these findings will enable us to begin understanding the important roles of AR actions in the regulation of female fertility and ovarian ageing, as well as providing insights into the role of AR actions in the androgen-associated reproductive disorder PCOS.

Characterizing the neuroendocrine and ovarian defects of androgen receptor-knockout female mice

Homozygous androgen receptor (AR)-knockout (ARKO) female mice are subfertile due to both intra- and extraovarian (neuroendocrine) defects as defined by ovary transplantation. Using ARKO mice, this study set out to reveal the precise AR-regulated pathways required for optimal androgen-regulated ovulation and fertility. ARKO females exhibit deficient neuroendocrine negative feedback, with a reduced serum luteinizing hormone (LH) response to ovariectomy (OVX) (P < 0.01). Positive feedback is also altered as intact ARKO females, at late proestrus, exhibit an often mistimed endogenous ovulatory LH surge. Furthermore, at late proestrus, intact ARKO females display diminished preovulatory serum estradiol (E2; P < 0.01) and LH (P < 0.05) surge levels and reduced Kiss1 mRNA expression in the anteroventral periventricular nucleus (P < 0.01) compared with controls. However, this reduced ovulatory LH response in intact ARKO females can be rescued by OVX and E2 priming or treatment with endogenous GnRH. These findings reveal that AR regulates the negative feedback response to E2, E2-positive feedback is compromised in ARKO mice, and AR-regulated negative and positive steroidal feedback pathways impact on intrahypothalamic control of the kisspeptin/GnRH/LH cascade. In addition, intraovarian AR-regulated pathways controlling antral to preovulatory follicle dynamics are disrupted because adult ARKO ovaries collected at proestrus have small antral follicles with reduced oocyte/follicle diameter ratios (P < 0.01) and increased proportions of unhealthy large antral follicles (P < 0.05) compared with controls. As a consequence of aberrant follicular growth patterns, proestrus ARKO ovaries also exhibit fewer preovulatory follicle (P < 0.05) and corpora lutea numbers (P < 0.01). However, embryo development to the blastocyst stage is unchanged in ARKO females, and hence, the subfertility is a consequence of reduced ovulations and not altered embryo quality. These findings reveal that the AR has a functional role in neuroendocrine regulation and timing of the ovulatory LH surge as well as antral/preovulatory follicle development.

Testosterone-dependent interaction between androgen receptor and aryl hydrocarbon receptor induces liver receptor homolog 1 expression in rat granulosa cells

Androgens play a major role in the regulation of normal ovarian function; however, they are also involved in the development of ovarian pathologies. These contrasting effects may involve a differential response of granulosa cells to the androgens testosterone (T) and dihydrotestosterone (DHT). To determine the molecular pathways that mediate the distinct effects of T and DHT, we studied the expression of the liver receptor homolog 1 (LRH-1) gene, which is differentially regulated by these steroids. We found that although both T and DHT stimulate androgen receptor (AR) binding to the LRH-1 promoter, DHT prevents T-mediated stimulation of LRH-1 expression. T stimulated the expression of aryl hydrocarbon receptor (AHR) and its interaction with the AR. T also promoted the recruitment of the AR/AHR complex to the LRH-1 promoter. These effects were not mimicked by DHT. We also observed that the activation of extracellular regulated kinases by T is required for AR and AHR interaction. In summary, T, but not DHT, stimulates AHR expression and the interaction between AHR and AR, leading to the stimulation of LRH-1 expression. These findings could explain the distinct response of granulosa cells to T and DHT and provide a molecular mechanism by which DHT negatively affects ovarian function.

Targeted loss of androgen receptor signaling in murine granulosa cells of preantral and antral follicles causes female subfertility

Ovarian granulosa cells display strong androgen receptor (AR) expression, suggesting a functional role for direct AR-mediated actions within developing mammalian follicles. By crossing AR-floxed and anti-Müllerian hormone (AMH)-Cre recombinase mice, we generated granulosa cell-specific androgen receptor knockout mice (GCARKO). Cre expression, assessed by lacZ activity, localized to 70%-100% of granulosa cells in most preantral to antral follicles, allowing for selected evaluation of granulosa cell AR-dependent actions during follicle development. Relative to wild-type (WT) females, GCARKO females were subfertile, producing a 24% reduction in the number of litters (P < 0.05) over 6 mo and an age-dependent decrease in total number of pups born, evident from 6 mo of age (P < 0.05). Follicle dynamics were altered in GCARKO ovaries at 3 mo of age, with a significant reduction in large preantral and small antral follicle numbers compared to WT ovaries (P < 0.05). Global premature follicle depletion was not observed, but increased follicular atresia was evident in GCARKO ovaries at 6 mo of age, with an 81% increase in unhealthy follicles and zona pellucida remnants (P < 0.01). Cumulus cell expansion was decreased (P < 0.01) and oocyte viability was diminished in GCARKO females, with a significant reduction in the percentage of oocytes fertilized after natural mating and, thus, in the rate of progression to the two-cell embryo stage (P < 0.05). In addition, compared with age-matched WT females, 6-mo-old GCARKO females exhibited significantly prolonged estrous cycles (P ≤ 0.05), suggesting altered hypothalamic-pituitary-gonadal feedback signaling. In conclusion, our findings revealed that selective loss of granulosa cell AR actions during preantral and antral stages of development leads to a premature reduction in female fecundity through reduced follicle health and oocyte viability.

Androgen actions and the ovary

Although androgens and the androgen receptor (AR) have defining roles in male reproductive development and function, previously no role in female reproductive physiology beyond testosterone (T) as the precursor in estradiol (E(2)) biosynthesis was firmly established. Understanding the role and specific mechanisms of androgen action via the AR in the ovary has been limited by confusion on how to interpret results from pharmacological studies, because many androgens can be metabolized in vivo and in vitro to steroids that can also exert actions via the estrogen receptor (ESR). Recent genetic studies using mouse models with specific disruption of the Ar gene have highlighted the role that AR-mediated actions play in maintaining female fertility through key roles in the regulation of follicle health, development, and ovulation. Furthermore, these genetic studies have revealed that AR-mediated effects influence age-related female fertility, possibly via mechanisms acting predominantly at the hypothalamic-pituitary axis in a dose-dependent manner. This review focuses on combining the findings from pharmacological studies and novel genetic mouse models to unravel the roles of ovarian androgen actions in relation to female fertility and ovarian aging, as well as creating new insights into the role of androgens in androgen-associated reproductive disorders such as polycystic ovarian syndrome.

The levels of 5alpha-dihydrotestosterone in follicular fluid in healthy and atretic ovine follicles

Dihydrotestosterone (DHT) induces follicular atresia under experimental conditions. However, whether it causes any antagonistic effect under natural condition is not known. In the present study, we investigated concentrations of DHT in follicular fluid and correlated them with concentrations of estradiol-17beta (E2) and its androgen substrates, androstenedione (A4) and testosterone (T), in healthy and atretic follicles of sheep. Merino ewes were treated twice with PGF2alpha (PG) to synchronize estrus. The ovaries were recovered at 14 days after the second PG (luteal phase) or 24h after the third PG given 14 days after the second PG (follicular phase). Follicles were dissected and their size and appearance were recorded. Follicular fluid was collected from follicles larger than 3.5mm and concentrations of E2, progesterone (P4), A4, T and DHT were determined by RIA. The inhibitory effect of DHT on conversion of T to E2 was tested in cultured granulosa cells. Appreciable levels of DHT were observed in the follicular fluid of ovine preovulatory follicles. The levels of DHT were much lower than those of E2, A4 and T, irrespective of physiological conditions of follicles. No difference was found in DHT concentration between healthy and atretic follicles. Dihydrotestosterone marginally inhibited aromatization of T in granulosa cells but this effect was only observed when the levels of DHT were 10 times higher than that of T in culture medium. These results indicate that DHT is present in ovine preovulatory follicles but its levels are not sufficient to exert any antagonistic effect on follicular development.

Female mice haploinsufficient for an inactivated androgen receptor (AR) exhibit age-dependent defects that resemble the AR null phenotype of dysfunctional late follicle development, ovulation, and fertility

The role of classical genomic androgen receptor (AR) mediated actions in female reproductive physiology remains unclear. Female mice homozygous for an in-frame deletion of exon 3 of the Ar (AR(-/-)) were subfertile, exhibiting delayed production of their first litter (AR(+/+) = 22 d vs. AR(-/-) = 61 d, P < 0.05) and producing 60% fewer pups/litter (AR(+/+): 8.1 +/- 0.4 vs. AR(-/-): 3.2 +/- 0.9, P < 0.01). Heterozygous females (AR(+/-)) exhibited an age-dependent 55% reduction (P < 0.01) in pups per litter, evident from 6 months of age (P < 0.05), compared with AR(+/+), indicating a significant gene dosage effect on female fertility. Ovulation was defective with a significant reduction in corpora lutea numbers (48-79%, P < 0.01) in 10- to 12- and 26-wk-old AR(+/-) and AR(-/-) females and a 57% reduction in oocytes recovered from naturally mated AR(-/-) females (AR(+/+): 9.8 +/- 1.0 vs. AR(-/-): 4.2 +/- 1.2, P < 0.01); however, early embryo development to the two-cell stage was unaltered. The delay in first litter, reduction in natural ovulation rate, and aromatase expression in AR(+/-) and AR(-/-) ovaries, coupled with the restored ovulation rate by gonadotropin hyperstimulation in AR(-/-) females, suggest aberrant gonadotropin regulation. A 2.7-fold increase (AR(+/+): 35.4 +/- 13.4 vs. AR(-/-): 93.9 +/- 6.1, P < 0.01) in morphologically unhealthy antral follicles demonstrated deficiencies in late follicular development, although growing follicle populations and growth rates were unaltered. This novel model reveals that classical genomic AR action is critical for normal ovarian function, although not for follicle depletion and that haploinsufficiency for an inactivated AR may contribute to a premature reduction in female fecundity.

Obligatory roles for follicle-stimulating hormone (FSH), estradiol and androgens in the induction of small polyfollicular ovarian cysts in hypophysectomized immature rats

Immature hypophysectomized (HYPOXD) rats develop large, polyfollicular ovarian cysts in response to unabated, combined stimulation by subovulatory doses of human chorionic gonadotropin (hCG) and highly purified ovine follicle-stimulating hormone (FSH). Further, circulating amounts of androstenedione (A4) and estradiol (E2), but not testosterone or dihydrotestosterone (DHT), change in parallel with the development of these cysts. To determine the potential roles of either A4 or E2 at the level of the ovary in the induction of ovarian cysts, pellets containing either (1) cholesterol (placebo; controls); (2) A4; or (3) E2 were administered subcutaneously (sc) to immature HYPOXD rats. Some of these animals also received either twice-daily sc injections of 1 IU hCG, or daily s.c. injections of 2 microg FSH, for 13 days. Ovaries and sera were harvested from all treatment groups on the morning of day 14 of the combined-hormone treatment schedule. As expected, ovaries from HYPOXD rats treated with placebo, A4, or E2 pellets (with or without hCG) failed to display antral follicles. Ovaries from HYPOXD rats treated with FSH and a placebo pellet displayed polyfollicular, atretic, small antral follicles with unstimulated thecal shells. In addition, the ovarian stromal-interstitial tissue had an unstimulated appearance. In contrast, ovaries from HYPOXD rats treated with FSH plus either A4 or E2 implants displayed stimulated stromal-interstitial tissue as well as small follicular cysts and precysts with stimulated thecal shells. The number of cysts and precysts observed in the largest ovarian cross-sections for animals treated with FSH + A4 (17.0 +/- 3.0) was less than that observed in the largest ovarian cross-sections for HYPOXD rats treated with FSH + E2 (40.2 +/- 10.1; p < 0.05). To determine if the development of ovarian cysts in response to FSH + A4 was due, at least in part, to the metabolism of A4 to E2, HYPOXD rats were treated with either (1) placebo pellets; (2) pellets containing dihydrotestosterone (DHT) which cannot be metabolized to estrogen; (3) E2 pellets plus DHT pellets (E2 + DHT); (4) FSH + DHT; or (5) FSH + E2 + DHT. The largest ovarian cross-sections from FSH + DHT-treated HYPOXD rats displayed 18.3 +/- 4.1 small follicles with a mean diameter of approximately 0.437 mm which possessed few granulosa cells. The thecal and stromal-interstitial tissues in these ovaries were unstimulated, which indicates that these small degenerating follicles were atretic rather than cystic. In contrast, the largest ovarian cross-sections from FSH + E2 + DHT-treated HYPOXD rats displayed 51.6 +/- 2.4 cysts with stimulated thecal shells and a mean diameter of approximately 0.634 mm. Further, these cysts were arranged in a "string of pearls" pattern and the ovarian stromal-interstitial tissue possessed a stimulated appearance. These data demonstrate a direct, unambiguous role at the level of the ovary for unabated tonic stimulation by FSH plus estrogen in the development of small polyfollicular cysts in HYPOXD rats. Further, the data also indicate that, at least in HYPOXD rats, combined, tonic stimulation by FSH plus estrogen and androgen is sufficient for the development of small, polyfollicular ovarian cysts in a "string of pearls" pattern. These observations are in distinct contrast to our previous observations that tonic stimulation by FSH + hCG results in the induction of large ovarian cysts in HYPOXD rats and provide tantalizing new insights regarding the potential importance of specific hormones at the level of the ovary in the induction of specific types of cystic follicles.

Direct Effects of Leptin on Mouse Reproductive Function: Regulation of Follicular, Oocyte, and Embryo Development

Because body condition can affect reproduction, research has focused on the role of leptin, a body condition signal, in regulation of reproductive function. Objectives of this study were to determine if leptin supplementation directly affects 1) ovarian follicle growth and function, 2) oocyte maturation, or 3) preimplantation embryo development. Follicles cultured in the presence of recombinant mouse leptin resulted in a significant decrease in rate of follicle, but not oocyte, growth in a dose-dependent manner, with higher doses of leptin inhibiting growth. Leptin was also found to significantly increase stimulated progesterone, estradiol, and testosterone production/secretion by cultured follicles in a dose-dependent manner, with higher concentrations of leptin significantly increasing steroidogenesis. Culture of fully grown cumulus-enclosed germinal vesicle-intact (GV) mouse oocytes in the presence of increasing concentrations of leptin (0, 12.5, 25, 50, 100 ng/ml) had no effect on germinal vesicle breakdown (GVBD) or development to metaphase II (MII). Similarly, fully grown denuded oocytes showed no difference in GVBD at any concentration of leptin. However, maturation of denuded oocytes with 100 ng/ml leptin resulted in significantly reduced development to MII compared with oocytes matured with 0 or 12.5 ng/ml leptin. Culture of one-cell mouse embryos in increasing concentrations of leptin had no effect on cleavage or blastomere degeneration at 24 h of culture. Exposure of embryos for the first 96 h of development to increasing concentrations of leptin did not significantly affect total or expanded blastocyst development or hatching of blastocysts from zona pellucida. These results indicate leptin directly enhances insulin and gonadotropin-stimulated ovarian steroidogenesis, compromises denuded oocyte maturation, yet has no direct effect on preimplantation embryo development.

Effects of aromatase inhibition on in vitro follicle and oocyte development analyzed by early preantral mouse follicle culture

In vivo studies on folliculogenesis have documented a relation among intrafollicular steroid content, follicle growth, and oocyte development. This study examined how profound changes in androgen/estrogen ratio would affect mouse in vitro follicular development. Arimidex, a potent follicular aromatase inhibitor was used for this purpose. Early preantral follicles were cultured for 12 days up to the preovulatory stage. Oocyte's meiotic maturation, spindle and chromosome configurations, in vitro fertilization and preimplantation embryo development were evaluated. Compared to controls, Arimidex reduced E2 concentration in follicle culture medium by a factor 1000, and an expected simultaneous accumulation of testosterone was measured in the conditioned medium. Arimidex treatment provoked a dose-dependent earlier differentiation of the granulosa cells as judged by an earlier antrallike cavity formation and slightly elevated basal progesterone secretion. Follicle survival exceeded 98% in all groups and all follicles responded normally to HCG/EGF addition on day 12 by cumulus mucification. By the HCG ovulatory challenge, progesterone output was reduced in Arimidex supplemented groups suggesting preovulatory luteinization. These results indicate that in vitro mouse follicles can develop normally under very low levels of estrogens and that a local androgen increase by a factor 3 is not atretogenic. Oocyte growth did not differ among culture conditions. Arimidex treatment induced a dose dependent enhancement of GVBD and polar body formation rate in response to HCG at the end of culture. Spindle and chromosome analyses demonstrated that in all groups, 90% of the oocytes which extruded a polar body had also reached the MII stage. While most of the cultured MII oocytes had a normal spindle and well aligned chromosomes, significantly less oocytes were fertilized in the groups cultured in the presence of Arimidex. Once fertilized, however, there was found to be no difference for preimplantation embryo development between controls and Arimidex treatment. These data suggest that in mice a pronounced estrogenic environment is not essential for in vitro folliculogenesis. Drastic changes in the intrafollicular steroid concentrations do not disrupt meiotic maturation nor compromise early preimplantation development, but adversely affect fertilization of in vitro grown oocytes.

Age-associated increases in serum follicle-stimulating hormone levels on estrus are accompanied by a reduction in the ovarian secretion of inhibin

In light of recent data demonstrating age-related alterations in the secretion and production of follicle-stimulating hormone (FSH) during the secondary FSH surge on estrus, the following study was conducted to determine the effects of age on periovulatory inhibin secretion. Ovarian venous blood was collected from groups of ether-anesthetized 3- and 7-month-old rats exhibiting 4-day estrous cycles at the following times: 1200 and 2400 h on proestrus and 1600 h on estrus. Following a 10-min collection period, a terminal blood sample was obtained from the abdominal aorta. Peripheral serum concentrations of luteinizing hormone (LH), FSH, estradiol-17 beta (E2), progesterone (P) and testosterone (T) were measured by RIA. Inhibin activity in ovarian venous serum (OVS) was assessed by the ability of OVS to suppress basal FSH secretion from dispersed pituitary cells during a 24-hour culture period. At 1200 h on proestrus, serum FSH (and LH) levels were higher in 7-month-old rats than in younger rats while the FSH-suppressing activity of OVS did not differ between age groups at this time. Bioassayable inhibin activity substantially declined between 1200 and 2400 h on proestrus in both groups. By 1600 h on estrus, serum FSH levels and inhibin secretion were higher and lower, respectively, in the older age group compared to 3-month-old rats. Significant increases in inhibin secretion between 2400 h on proestrus and 1600 h on estrus were observed only in younger rats.(ABSTRACT TRUNCATED AT 250 WORDS)

Animal models for study of polycystic ovaries and ovarian atresia

In the human, polycystic ovaries are generally accompanied by normal or elevated levels of serum LH, normal or slightly depressed FSH and by high levels of circulating estrogens and androgens. If the excess androgen secretion is reduced by one of several methods, ovulatory cycles are usually restored. Several animal model systems have been proposed for the study of the pathophysiology of the polycystic ovarian syndrome. These include neonatal androgenization, hCG administration to hypothyroid rats, injection of estradiol valerate and maintaining animals in constant light. In a model developed in this laboratory, pubertal or adult rats were treated with the weak androgen, dehydroepiandrosterone (DHA), to induce polycystic ovaries. This treatment also altered the blood levels of LH and FSH but the effect on gonadotropins and on the formation of the degenerative follicles was fully reversed following discontinuation of the androgen injections. The polycystic ovaries of the DHA-treated animals were steroidogenically more active than controls raising the possibility that the DHA was acting directly on the ovary in addition to an action on the pituitary-hypothalamus axis. In order to study the direct effect of androgens on the ovary, another animal model was developed in which immature, hypophysectomized rats were injected with pregnant mare serum gonadotropin (PMSG) to initiate follicular growth followed by a single injection of dihydrotestosterone (DHT). The androgen caused follicular atresia and decreased the number of ova shed in response to ovulation induction with hCG. The suppressive effects of DHT were entirely prevented by concomitant treatment with estradiol. The studies with DHT were continued using another batch of PMSG, but the DHT-induced increase in the rat of atresia and suppression of induced ovulation were no longer seen. However, when this same batch of PMSG was given with estrogen or with the antiandrogen flutamide, there was less atresia and the growth of follicles was actually enhanced. Based on these studies, it was postulated that the second batch of PMSG had greater LH activity than the first preparation and that the LH has stimulated endogenous androgen production. The ovarian follicles which appeared to be most susceptible to this DHT effect were small to medium in size and had a low capacity to synthesize estrogen. This possibility was confirmed in another animal model system in which immature rats were injected with PMSG and 4 separate injections of DHT and then sacrificed at several time points over the next 8 days.(ABSTRACT TRUNCATED AT 400 WORDS)

Luteinizing hormone receptor induction in dispersed granulosa cells requires estrogen

Studies on granulosa cell responses in vitro have routinely utilized cell preparations in which intercellular gap-junctions are maintained. The present study was conducted to determine if disruption of these junctions, prior to culture, would affect subsequent follicle-stimulating hormone (FSH)-stimulated luteinizing hormone (LH) receptor induction on these cells. Granulosa cells were expressed from ovaries of diethylstilbestrol (DES)-primed immature rats after a short incubation of the excised ovaries in culture medium alone or medium containing 6.8 mM EGTA. The latter procedure disrupts gap-junctions between granulosa cells thus providing a predominantly mono-dispersed cell suspension. The two cell preparations were cultured, separately, for 72 h in sterile polypropylene tubes in media containing either FSH or FSH plus various steroids (estradiol, testosterone, or 5 alpha-dihydrotestosterone (DHT)). LH receptor content of cells was determined at 72 h of culture. Both the cell yield and the proportion of viable cells obtained were enhanced by the EGTA pretreatment. LH receptors were induced in all FSH-containing cultures of non-dispersed granulosa cells. In the dispersed cell cultures, FSH alone failed to induce LH receptors. The inclusion of either estradiol or testosterone but not DHT with FSH, however, restored LH receptor induction to levels comparable to non-dispersed cultures. LH receptors were not induced in cultures of either cell preparation with steroids alone. Aromatase activity, however, was stimulated in both cell preparations by FSH alone. These results suggest that cell-cell communication may be necessary for LH receptor induction in granulosa cells and that estradiol (or an aromatizable androgen) can promote intercellular interactions if this communication has been disrupted.