Soluble intercellular adhesion molecule-1 in ovarian follicles: production by granulosa luteal cells and levels in follicular fluid

OBJECTIVE

To determine the concentration of the soluble form of intercellular adhesion molecule (ICAM)-1 in granulosa luteal cell-conditioned media and in follicular fluid (FF).

DESIGN

Granulosa cells and FF samples were obtained at the time of oocyte retrieval for IVF. In 10 women, a total of 33 fluids were obtained from individual follicles, whereas in 70 women, the follicular aspirates were pooled.

SETTING

Clinica "L. Mangiagalli" and Reproductive Center, San Raffaele Hospital, Milan, Italy.

PATIENT(S)

Eighty women referred for IVF for tubal factor or male factor infertility.

INTERVENTION(S)

Women underwent ovarian hyperstimulation.

MAIN OUTCOME MEASURE(S)

Soluble ICAM-1 was measured by an ELISA, and its levels were correlated with follicular size, the number of retrieved oocytes, and the number of follicles with a diameter of >15 mm.

RESULT(S)

The concentration of soluble ICAM-1 in granulosa luteal cell-conditioned media was 17.8 +/- 1.8 ng/5 x 10(5) cells. Interleukin-1beta can stimulate soluble ICAM-1 release in a dose-dependent manner. A significant positive correlation was demonstrated between levels of soluble ICAM-1 in pooled FF and the number of retrieved oocytes or the number of follicles with a diameter of >15 mm.

CONCLUSION(S)

Soluble ICAM-1 can be released by granulosa luteal cells and can be detected in FF after ovarian hyperstimulation. Levels of soluble ICAM-1 in FF correlate directly with some indices of ovarian function.

Characterization of messenger ribonucleic acid expression for prostaglandin F2 alpha and luteinizing hormone receptors in various bovine luteal cell types

LH and prostaglandin F2 alpha (PGF2 alpha) control the life span and function of the corpus luteum (CL). Nevertheless, identification of the various cell types (steroidogenic and nonsteroidogenic) expressing the receptors for these hormones remains controversial. In this study we characterized LH and PGF2 alpha receptor (r) expression in the various luteal cell types using quantitative reverse transcription-polymerase chain reaction. We found, in agreement with previously described functions of PGF2 alpha, that the two steroidogenic cell types, as well as luteal endothelial cells, expressed PGFr. In contrast, LHr was mainly expressed by small luteal cells. A similar pattern of PGFr and LHr expression was observed in steroidogenic cells luteinized in vitro and in cells derived from the mature CL. The expression of these two receptors was inversely affected by increased levels of cAMP (achieved by incubating cells with varying doses of forskolin); LHr expression was down-regulated by 50% in the presence of 10 microM forskolin (p < 0.05), while an increase was observed in PGFr expression. In granulosa-derived luteal cells, maximal expression of PGFr was higher (approximately by 3-fold, p < 0.05) than in the theca-derived luteal cells. PGF2 alpha, mimicking its in vivo effect, markedly down-regulated LHr expression in thecaderived luteal cells, abolishing expression at a concentration of 100 ng/ml. In summary, these studies depict cAMP and PGF2 alpha as major regulators of PGFr and LHr expression in the two steroidogenic cell types. All three major cell types of the CL (steroidogenic and endothelial) express PGFr. LHr mRNA, on the other hand, was detected mainly in small luteal cells. Such broad cellular distribution of PGFr may highlight the significant role played by this prostaglandin in the bovine CL.

Effects of estradiol and an aromatase inhibitor on progesterone production in human cultured luteal cells

The human corpus luteum produces both estradiol and progesterone. It is well known that there are both autocrine and paracrine systems for the regulation of the corpus luteum and that estradiol regulates the progesterone production of the corpora lutea of some other species. To assess the direct effects of estrogen on human luteal function, we performed cell culture experiments. A low concentration of estradiol, almost equal to the amount of estradiol produced by human cultured luteal cells, directly stimulated progesterone production. 4-Cyclohexylaniline, an aromatase inhibitor, significantly reduced both progesterone production and estradiol production. Levels of estradiol higher than the levels that cultured human luteal cells themselves produced significantly reduced basal progesterone production and also significantly reduced human chorionic gonadotropin (hCG), forskolin and dibutyryl-cyclic AMP-stimulated progesterone production. According to these data, high doses of estradiol produced a luteolytic action which widely inhibited the steroidogenesis process. In conclusion, our results indicated that estradiol in part regulates progesterone production physiologically and blocks progesterone production in a pharmacological or pathological state in the human corpus luteum.

Interaction of prostaglandin F2alpha and gonadotropin-releasing hormone on progesterone and estradiol production in human granulosa-luteal cells

This study examined the effects of prostaglandin-F2alpha (PGF2alpha), GnRH, and their interactions on steroidogenesis in human granulosa-luteal cells (GLCs). Human GLCs collected from in vitro fertilization patients were cultured for one or eight days, followed by a 24-h treatment period, after which media were collected and radioimmunoassayed for progesterone and estradiol. In the first experiment, GLCs were treated with vehicle, PGF2alpha (10(-9) M), GnRH (10(-6) M), or PGF2alpha plus GnRH, with or without hCG (1 IU/ml). Neither PGF2alpha nor GnRH alone had a significant effect; however, the combination of PGF2alpha plus GnRH significantly stimulated steroidogenesis. Similarly, co-application enhanced the luteolytic effects of PGF2alpha. In a second experiment, PGF2alpha and GnRH concentration-response curves were crossed into a matrix of 49 separate treatments. Responses were plotted in three-dimensions and as two-dimensional "slices" that were analyzed statistically. In the presence of high concentrations of GnRH (10(-6) M), PGF2alpha stimulated progesterone production in a biphasic manner, as middle concentrations significantly stimulated (10(-9) M) whereas low and high concentrations did not. In the presence of middle concentrations of PGF2alpha (10(-9) M), GnRH significantly stimulated progesterone production in a linear concentration-dependent manner. Similar complexities were seen with respect to estradiol response. Thus, in the human GLC, GnRH potentiates the luteolytic effects of PGF2alpha, while it acts as a permissive factor for the luteotropic effects. Furthermore, we have revealed the complex interaction of these hormones using a three-dimensional experimental design.

Regulation of insulin-like growth factor-binding protein-1 and progesterone secretion from human granulosa-luteal cells: effects of octreotide and insulin

OBJECTIVE

To examine the effects of the synthetic somatostatin-analogue octreotide and human recombinant insulin on the release of insulin-like growth factor binding protein-1 (IGFBP-1) and P from human granulosa-luteal cells.

DESIGN

Primary culture of human granulosa-luteal cells.

SETTING

Academic research laboratory.

PATIENT(S)

Women undergoing oocyte retrieval for IVF-ET because of tubal infertility.

INTERVENTION(S)

Octreotide or insulin were added to the cultures; sampling of culture medium was performed after 48 hours.

MAIN OUTCOME MEASURE(S)

Insulin-like growth factor binding protein-1 and P.

RESULT(S)

Octreotide significantly inhibited IGFBP-1 (58.8% compared with controls) and P release (66.1% compared with controls). Insulin abolished IGFBP-1 release while stimulating P release (200.7% compared with controls). There was a significant and positive correlation between IGFBP-1 and P levels.

CONCLUSION(S)

Octreotide and insulin have a significant effect on human granulosa-luteal cell function in terms of IGFBP-1 and P release. Our results suggest a local ovarian mechanism for the recently observed effects of octreotide in the treatment of women with polycystic ovary syndrome.

Follicle-stimulating hormone and intracellular second messengers regulate steroidogenic acute regulatory protein messenger ribonucleic acid in luteinized porcine granulosa cells

Ligand- and second messenger-regulated expression of the gene for steroidogenic acute regulatory protein (StAR) was evaluated in luteinized porcine granulosa cells. For comparison, cytochrome P450 side-chain cleavage (P450scc) was examined. Northern hybridization with homologous cDNA probes demonstrated three StAR mRNA species, of 2.7, 1.6, and 0.8 kilobases (kb), with the smallest variably present, and a single P450scc band at 1.9 kb. FSH elevated both STAR and P450scc messages in a dose-dependent manner over 6 h and continually stimulated both over 24 h (p < 0.001). STAR message induction depended on transcription, as did that of P450scc. Over 6 h, actinomycin D eliminated constitutive StAR message and reduced that of P450scc by two thirds, indicating briefer persistence of StAR. Pretreatment with cycloheximide prevented FSH induction of StAR and P450scc mRNA, implicating intermediate protein synthesis in expression of both genes. Dibutyryl cAMP caused time-dependent increases in StAR and P450 mRNAs over 24 h (p < 0.001), indicating the importance of the protein kinase A (PKA) pathway in their gene expression. Activation of the protein kinase C (PKC) pathway by a phorbol ester eliminated FSH induction of STAR mRNA increases (p < 0.01) while only reducing P450scc induction (p < 0.05). Thus, StAR gene expression, as reflected in mRNA abundance, is regulated by FSH via the PKA pathway and is dependent on transcription and translation. Conversely, the PKC pathway inhibits induction of these important steroid synthetic genes in luteinized granulosa cells.

Further evidence of increased aromatase activity in granulosa luteal cells from polycystic ovary

This study evaluated the effect of atamestane (a competitive inhibitor of P-450 aromatase) on granulosa luteal cells from polycystic and normal ovaries. Treatment with atamestane (10 micromol/l) determined a strong inhibition of basal aromatase activity in both types of cells; however, its effect was markedly more pronounced in granulosa cells from normal ovary than in granulosa cells from polycystic ovaries (PCO; P < 0.01). Concomitant treatment with insulin (25 microg/ml) and increasing doses of atamestane (0.01-10 micromol/l) caused a dose-dependent inhibition of insulin-stimulated aromatase activity, but again with marked differences between the two types of cells. In granulosa cells from PCO, the minimal effective dose of atamestane was 1 micromol/l and it had an EC50 of 2.23 +/- 0.4 micromol/l and a maximal inhibitory effect of 75%; in granulosa cells from normal ovary, the minimal effective dose of atamestane was 0.01 micromol/l, the EC50 was 0.4 +/- 0.07 micromol/l, and the maximal inhibitory effect was 94%. Significant differences were observed between the different cells at all the studied dose points. Reversibility studies showed that resumption of aromatase activity in granulosa cells from PCO is basally greater and more inducible with insulin treatment. This study provides further evidence of an increased in-vitro function of the aromatase complex in granulosa cells from PCO, that could be induced by an altered cellular autoregulation.

Simulation of human luteal endocrine function with granulosa lutein cell culture

Human granulosa cells collected from in vitro fertilization have previously been cultured to provide a system to simulate the granulosa lutein cells of the corpus luteum. In most of these systems, the cultures have been relatively short term, and attempts to simulate the normal pattern of hormone production observed during the luteal phase of the cycle have not been reported. Additionally, the hormone relaxin has generally been absent from the endocrine analysis of these systems. In this report, methods were used that supported secretion of ovarian steroids and relaxin that mimics the profiles of these hormones in vivo. This system was used to observe the endocrine responses of the granulosa lutein cells to three different protocols of CG administration designed to mimic the normal luteal phase, early pregnancy, and early pregnancy followed by pregnancy loss. The normal luteal phase was simulated by a constant baseline (0.02 IU/mL) CG model to simulate a nonconceptive cycle (baseline). The second model was baseline CG until day 8 of culture, followed by daily doubling from days 9-17 to simulate an early pregnancy (rescue-plateau). CG concentrations were then held constant from days 17-20 (5.12 IU/mL). A third model (rescue-drop) was used that was identical to the early pregnancy model except that on day 17 CG was returned to baseline concentrations (0.02 IU/mL) to simulate an early pregnancy loss. Baseline CG stimulation resulted in profiles of estrogen, progesterone, and relaxin secretion in culture that were closely related to secretory profiles previously reported in serum during the nonconceptive luteal phase. The timing of appearance of relaxin secretion and later declines in steroid and relaxin secretion paralleled that observed in serum. In the CG rescue protocols, ovarian steroids rose in response to daily doubling of CG and fell when CG either plateaued or fell. Relaxin did not show an increase in response to increasing CG, but its secretion did not drop when CG concentrations plateaued or dropped. This cell culture system model mimics the profile of ovarian steroids and relaxin seen in serum during the nonconceptive luteal phase, although the relative magnitude of the hormones was not the same as seen in vivo. It was also used to investigate responses to luteal rescue protocols designed to simulate early pregnancy and pregnancy loss. This culture system may be useful to study differences in endocrine response in granulosa cells collected from different patients and to provide information of clinical relevance. This culture system provides a model to study luteal function and its response to different protocols of luteal rescue and thus may provide insight into early pregnancy and pregnancy loss.

Interaction of mouse placental lactogens and androgens in regulating progesterone release in cultured mouse luteal cells

Pituitary hormones are essential for the maintenance of the corpus luteum in the pregnant mouse during the first half of gestation. Thereafter, hormones from the placenta take over the luteotropic role of the pituitary hormones. Mouse placental lactogen-I (mPL-I) and mPL-II, two PRL-like hormones produced in the placenta, are probably necessary for the maintenance of the corpus luteum in the latter half of pregnancy. A culture system of luteal cells from pregnant mice was developed to investigate the role of hormones from the placenta that may be important for the function of the corpus luteum. Mice were killed on days 10, 14, and 18 of pregnancy, and the corpora lutea were excised from the ovaries and digested in 0.1% collagenase, 0.002% DNase for 1 h. The resulting luteal cell suspension was plated onto 96-well plates coated with fibronectin (1 x 10(5) cells/well) and cultured for 1-3 days. Medium was changed daily. The cells were treated with various concentrations and combinations of mPL-I, mPL-II, mouse PRL, androstenedione, dihydrotestosterone, 17beta-estradiol (E2), testosterone, hydroxyflutamide, cycloheximide, actinomycin D, and fadrozole to study the effects of these different treatments on progesterone (P4) production. The three lactogens (mPL-I, mPL-II, and mouse PRL) all stimulated the release of P4 from the luteal cells. The potency of the lactogens was similar and did not depend on the stage of pregnancy at which the luteal tissue was obtained. However, the responsiveness of the cells to all hormone-stimulated P4 release was gradually reduced the later in pregnancy the tissue was collected. Androgens also stimulated the release of P4 from the luteal cells, and when administered together, the lactogens and the androgens acted synergistically to stimulate P4 release. The androgens acted directly but not through conversion to E2, as determined by the findings that 1) the effects of the androgens could not be reproduced by E2 administration, 2) nonaromatizable androgen dihydrotestosterone was as effective as aromatizable androgens, and 3) aromatase inhibitor did not prevent the action of the androgens to stimulate the P4 release. The effect of the androgens on the P4 release was rapid, occurring within 15 min of hormone administration. It was not prevented by inhibitors of protein and RNA synthesis, and the intracellular androgen receptor antagonist hydroxyflutamide did not affect the androgen action. Therefore, the androgen effects were not mediated through the intracellular androgen receptor and de novo protein synthesis was not needed for androgen-stimulated P4 release.

Activation of elements of the phosphatidylinositol pathway in the primate corpus luteum by prostaglandin E2

The current study was designed to examine the effects of prostaglandin (PG) E2 on progesterone production by primate luteal cells collected during the late luteal phase. PGE2 inhibited basal and human chorionic gonadotrophin (HCG)-stimulated progesterone production (P < 0.01) in late luteal phase corpora lutea. The ability of PGE2 to activate a second messenger system (phosphatidylinositol pathway) in corpora lutea of rhesus monkeys was also assessed. PGE2 significantly increased the accumulation of inositol phosphates (P < 0.05). This stimulation was not apparent in the early luteal phase but was manifested in the mid-late luteal phase. PGE2 also caused a rapid, yet transient, increase (P < 0.01) in intracellular free calcium ion concentrations ([Ca2+]i) in a large proportion of primate luteal cells. The proportion of luteal cells that responded to PGE2 with an increase in [Ca2+]i was smaller (P < 0.05) in corpora lutea collected during the early luteal phase (12%) in comparison with those collected during the latter half of the luteal phase (63-66%). Changes in [Ca2+]i in response to PGE2 were similar in small and large luteal cells. This study demonstrates that PGE2 activates elements of the phosphatidylinositol pathway in primate corpora lutea. This activation is augmented as the luteal phase progresses. Thus, the inhibitory effects of PGE2 on luteal progesterone production observed in the late luteal phase are associated with activation of elements of the phosphatidylinositol pathway.

Prostaglandin E2 induces inhibin alpha- and beta A-subunit mRNA and secretion of dimeric inhibin A in cultured human granulosa-luteal cells

Prostaglandins (PG) E2 and F2 alpha are produced by the human corpus luteum in significant amounts and they are known to exert local luteotrophic and luteolytic effects respectively. The present study determined how PGE2 and PGF2 alpha are involved in the regulation of inhibin A, a granulosa cell-derived glycoprotein hormone that has an endocrine inhibitory effect on hypophyseal gonadotrophin production and a local stimulatory action on thecal cell androgen secretion. The effects of PGE2 and PGF2 alpha on inhibin alpha- and beta A-subunit mRNAs levels and on the secretion of dimeric inhibin A were studied in cultures of human granulosa-luteal cells obtained from patients undergoing an in-vitro fertilization programme. We found that PGE2 induced mRNA of inhibin alpha- and beta A-subunits in a time- and concentration dependent manner, whereas PGF2 alpha had no clear effect. In contrast to the rapidly and transiently induced beta A-subunit mRNA, alpha-subunit mRNA accumulation was stimulated with slower kinetics by PGE2 in a protein synthesis-dependent manner; this was also observed for the mRNA of the cytochrome P450scc enzyme. In the medium of cells cultured for 24 h with PGE2 (1 x 10(-6) M), 1.3-1.6-fold increase (P < 0.05) above basal values in secreted dimeric inhibin A was observed. The results suggest that PGE2 is an important inducer of inhibin A production in granulosa cells and that a local action of PGE2 may partially explain the increase in circulating inhibin A observed during the midluteal phase of the human menstrual cycle.

Expression of steroidogenic acute regulatory protein (StAR) in the human ovary

Expression of steroidogenic acute regulatory protein (StAR) messenger ribonucleic acid (mRNA) in human ovary and cultured proliferating granulosa-lutein cells, theca interna cells, and luteinized granulosa cells was examined. The StAR transcripts were restricted in situ to theca of preovulatory follicles and luteinized granulosa and thecal cells of the corpus luteum. The cyclic nucleotide analog, 8-bromo-cAMP (8-Br-cAMP), increased StAR mRNA in all cell types studied by a process requiring on-going RNA and protein synthesis. Phorbol myristate acetate prevented the stimulatory effects of 8-Br-cAMP. In proliferating granulosa-lutein cells, 8-Br-cAMP increased StAR gene transcription and did not significantly affect StAR mRNA stability. Forskolin treatment was also found to increase the expression of a human StAR proximal promoter-luciferase fusion gene transfected into the proliferating granulosa-lutein cells. We conclude that 1) the StAR gene is expressed in the most steroidogenic compartments of the human ovary; 2) induction of StAR gene transcription by cAMP, produced in response to the LH surge, accounts for the appearance of StAR transcripts in luteinized granulosa cells; and 3) the effects of cAMP are antagonized by activators of protein kinase C.

Insulin-like growth factor (IGF)-I and IGF-II stimulate progesterone production by human luteal cells: role of IGF-I as mediator of growth hormone action

OBJECTIVE

To examine the possible direct effect of insulin-like growth factor (IGF)-I and IGF-II on basal and hCG-stimulated P production by cultured human luteal cells. The possible role of IGF-I as mediator of GH action on luteal steroidogenesis also was investigated.

DESIGN

Cultures of human luteal cells from early and midluteal phase.

SETTING

All corpora lutea were obtained from the Obstetrics and Gynecology Department of the Universita Cattolica, a public care center.

PATIENTS

Eight nonpregnant women between 35 and 47 years of age underwent surgery for various nonendocrine disorders such as leiomyomatosis.

INTERVENTIONS

Corpora lutea were obtained at the time of hysterectomy.

MAIN OUTCOME MEASURES

Luteal cells were incubated with IGF-I or IGF-II with or without hCG at different concentrations. Growth hormone also was used alone and with an anti-IGF-I-antibody.

RESULTS

We found that IGF-I and IGF-II were able to stimulate directly the P production at all used concentrations and that both of them significantly amplified the steroidogenic hCG effect. Finally, IGF-I was shown to mediate the positive GH action on P synthesis.

Cytokine induction of heat shock protein in human granulosa-luteal cells

The infiltration of leukocytes is a characteristic feature of luteolysis in humans. Leukocytes are known to generate physiological inducers of cell stress such as cytokines which have been implicated as mediators of functional luteal regression. In cells exposed to stress, a response characterized by an increase in heat shock protein (HSP) synthesis occurs. Recently, the induction of HSP-70 in rat luteal cells has been shown to inhibit luteinizing hormone (LH) and cAMP-sensitive progesterone production, possibly by interfering with the translocation of cholesterol to the mitochondrial cytochrome P450scc. We therefore investigated whether HSP-70 is induced in human granulosa-luteal cells and its relationship to steroidogenesis. [35S]Methionine labelling showed an increase in a 70 kDa protein after heat treatment which was demonstrated to be HSP-70 by Western analysis using monoclonal antibodies against the constitutive and inducible forms of HSP-70. Induction of HSP-70 in human granulosa-luteal cells was also seen with interferon (IFN) gamma (10 ng/ml), tumour necrosis factor (TNF)-alpha (100 ng/ml) and a combination of IFN gamma/TNF-alpha (10/50 ng/ml). Interleukin-1 beta (IL-1 beta) (30 ng/ml) showed minimal induction of HSP-70 above control values. An increase in activated heat shock factor, which binds to the heat shock transcriptional control element, was detected after heat shock, IFN/TNF, and IFN treatment. Coincident with the induction of HSP-70 by heat shock was the inhibition of progesterone production compared with non-shocked granulosa-luteal cells. Heat shock inhibition of progesterone synthesis was partially reversed by the cell- and mitochondria-permeant cholesterol analogue, 22R-hydroxycholesterol. Cell viability was unaffected by heat treatment. White blood cell-depleted granulosa-luteal cell cultures treated with IFN demonstrated a significant reduction in progesterone production. Treatment with IFN/TNF, TNF, and IL-1 also decreased progesterone secretion, although statistical significance was not achieved. These findings provide evidence that a stress response occurs in human granulosa-luteal cells in response to heat and cytokines. The inhibition of gonadotrophin-sensitive steroidogenesis coincident with the induction of HSP-70 synthesis by physiological agents which are present in the corpus luteum implicates HSP-70 as a potential mediator of luteolysis in the human.

Long chain polyunsaturated fatty acids and bovine luteal cell function

Experiments were conducted to determine the effects of exogenous polyunsaturated fatty acids (PUFA) on the production of progesterone and prostanoids by dispersed bovine luteal cells and to characterize endogenous luteal fatty acids throughout the estrous cycle. The addition of eicosapentaenoic acid (20:5, n3) resulted in a dose-dependent reduction of progesterone production and an increase in production of prostaglandin (PG) F2 alpha (PGF2 alpha) (p < 0.05). Nordihydroguaiaretic acid abolished the inhibitory effects of 20:5, n3 on progesterone production, while indomethacin did not alter these effects. The addition of 10 micrograms docosahexaenoic acid (22:6, n3) resulted in a suppression of progesterone synthesis (p < 0.05) and reduced PGF2 alpha synthesis. The addition of 0.1, 1, and 10 micrograms docosatetraenoic acid (22:4, n6) inhibited basal progesterone production, whereas only the highest dose decreased LH-stimulated synthesis of progesterone. The addition of 22:4, n6 resulted in increased PGF2 alpha synthesis (p < 0.05) and in lowered synthesis of prostacyclin (p < 0.05). Variations in luteal fatty acids were confirmed by an experiment in which endogenous fatty acids were characterized throughout the estrous cycle. The percentages and ratios of PUFA were altered throughout the estrous cycle. In summary, PUFA have potent inhibitory effects on the production of progesterone and PGI2 in vitro and may play a role in bovine luteal cell function by mechanisms yet to be determined.

Subclinical changes in luteal function in cynomolgus monkeys with moderate blood lead levels

The objective of the present study was to investigate luteal function in cynomolgus monkeys (n = 32), aged 15-20 years with blood lead levels (BLLs) in the range of < 3.0 micrograms dl-1 (control, n = 20), 10-15 micrograms dl-1 (low, n = 7) and 25-30 micrograms dl-1 (moderate, n = 5). Sampling was performed daily beginning with day 10 of the menstrual cycle and concluding on the first day of the subsequent menstrual cycle. Circulating levels of oestradiol (E2), progesterone (P4) and 20 alpha-hydroxyprogesterone (20-OHP) were normalized to the day of the ovulatory E2 surge. The area under the concentration curve (AUC) for P4 was significantly lower in monkeys with moderate BLLs compared to the control group (P = 0.04). The number of days for which circulating levels of P4 were greater than 1.0 ng ml-1 were also significantly fewer (P = 0.03) in monkeys with moderate BLLs compared to controls. There was no statistical evidence of a lead effect on circulating levels of E2, 20-OHP or menstrual cycle characteristics. These data suggest that chronic lead exposure suppresses corpora luteal production of P4 in the monkey at circulating BLLs lower than previously reported and relevant to humans with occupational exposure to lead.

Endocrine regulation of ascorbic acid transport and secretion in luteal cells

Luteal ascorbic acid depletion by LH and prostaglandin (PG) F2 alpha is well known, but how such depletion occurs is not. We therefore investigated the nature and regulation of ascorbic acid uptake and depletion in the rat CL and luteal cells. In vivo studies showed that blockade of steroidogenesis by aminoglutethimide prevented ascorbate depletion by LH, but not PGF2 alpha. Also, the time course for half-maximal depletion of ascorbic acid in vivo in response to PGF2 alpha was extremely rapid (2-3 min) compared to that known for LH (60 min). Thus, ascorbate depletion by LH and PGF2 alpha appears to occur by different mechanisms. In luteal cells, ascorbate uptake was energy-, sodium-, and microfilament-dependent with a Michaelis constant (Km) of 33 microM, similar to that reported for other cells. In contrast to findings for other cells, PGF2 alpha was found to be a potent and rapid inhibitor of ascorbate uptake with a half-maximal inhibition (IC50) of about 5 nM in luteal cells. Ascorbate uptake was unaffected by LH, PGE2, glucose, bromo-cAMP, progesterone, phorbol ester, ionomycin, hydrogen peroxide (H2O2), or aminoglutethimide. Also novel was the finding that luteal cell secretion of ascorbic acid was rapidly and potently stimulated by PGF2 alpha (IC50 about 5 nM), an effect mimicked by LH, H2O2, generators of reactive oxygen, calcium ionophore, and cytochalasin B. Basal release of ascorbic acid was energy-dependent, as secretion was blocked by a mitochondrial uncoupler and lowered temperature. Phorbol ester, bromo-cAMP, progesterone, aminoglutethimide, and ouabain had no effect on ascorbic acid secretion in luteal cells. These findings indicate that the secretion of ascorbic acid induced by PGF2 alpha, and possibly LH, may be mediated by calcium, reactive oxygen, and cytoskeletal changes. The ability of PGF2 alpha to inhibit ascorbate transport and to stimulate secretion implicates these processes as the basis for the rapid depletion of ascorbic acid in the CL. Ascorbate depletion by LH is associated with stimulation of steroidogenesis and an increase in ascorbic acid secretion.

Androgen production by monkey luteal cell subpopulations at different stages of the menstrual cycle

Androgens produced by the primate corpus luteum (CL) serve as precursors for estrogen synthesis; moreover, detection of androgen receptors in luteal tissue suggests a regulatory role within the CL. To determine the cellular source(s) and agonist regulation of androgen production during the lifespan of the primate CL, luteal tissues were collected from rhesus monkeys in the early (days 3-5 post-LH surge), mid (days 7-8), mid-late (days 11-12), and late (days 14-15) luteal phase of the menstrual cycle. Collagenase-dispersed cells (i.e., mixed cells) were analyzed by flow cytometry based on light scatter properties and sorted into populations of small (< or = 15 microns) and large (> 20 microns) luteal cells. Cells (n = 4 animals/stage) were incubated in Ham's F-10 and 0.1% BSA for 3 h at 37 C with or without hCG (100 ng/mL), PGE2 (14 mumol/L), or dibutyryl cAMP (dbcAMP; 5 mmol/L), and androstenedione (A4) and testosterone were measured. Basal A4 production by large cells was markedly higher (P < 0.05) than that by small cells (e.g. mid-late luteal phase, 821 +/- 188 vs. 69 +/- 25 pg/mL.5 x 10(4) cells/3 h; mean +/- SEM), whereas that by mixed cells was intermediate (317 +/- 205 pg/mL). In the early luteal phase, hCG stimulated A4 synthesis by mixed (1.6-fold; P < 0.05) and large (3.1-fold; P < 0.05) luteal cells, but not by small cells (1.3-fold). By the mid-late luteal phase, hCG did not increase A4 production by any cell type, although hCG responsiveness returned to large cells (2.0-fold increase; P < 0.05) by the late luteal phase. PGE2 responsiveness by cell types was similar to that of hCG, except large cell responsiveness did not return in the late luteal phase. In all cell types, dbcAMP stimulated the largest increase in A4 levels; in the mid-late luteal phase, small and large cells responded to dbcAMP with 8.2- and 3.0-fold increases (P < 0.05) in A4 production, respectively. When luteal cells were incubated with the steroidogenic substrates, 17 alpha-hydroxyprogesterone or 17 alpha-hydroxypregnenolone (1 mumol/L), large cells produced much more (P < 0.05) A4, testosterone, estrone, and estradiol than small cells. Both substrates elicited similar patterns of androgen production, with A4 synthesis predominant in all luteal cell types. Thus, cell subpopulations in the primate CL can be distinguished by their ability to produce androgen and estrogen. Changes in agonist-responsive androgen production may influence the local steroid milieu and function of the CL during the menstrual cycle.

The possible involvement of LH/hCG induced mitochondrial proteins in the regulation of steroidogenesis in bovine luteal cells

In previous studies we described the synthesis of three mitochondrial proteins (A, B and C) in response to acute in vitro stimulation by lutropin of small bovine luteal cells. Protein A had a molecular weight of 28 kDa and an isoelectric point (pI) of 6.7. Proteins B and C had a molecular mass of 27 kDa and pI of 6.2 and 6.4, respectively. The appearance of these proteins was prevented by 100 microM cycloheximide. In the present study, we have shown that the time course of synthesis of protein A and its hCG dose-response closely parallel the increase in progesterone production. The induction by hCG of protein A was already observed after a 5 min incubation. Pulse chase experiments by addition of excess unlabelled methionine after prelabelling with [35S]methionine indicated that its half-life was approximately 15-20 min. Study of 32P labelled phosphate incorporation into individual proteins and treatment by alkaline phosphatase of [35S]methionine-labelled proteins demonstrated that none of the three proteins A, B or C was a phosphoprotein. Localization of protein A in mitochondria, at the site of the rate limiting step in steroidogenesis, and the high degree of correlation between its 35S labelling and progesterone production argue in favour of its involvement in the acute regulation of steroidogenesis.

Interleukin-1 alpha and -beta modulation of luteinized human granulosa cell oestrogen and progesterone biosynthesis

This study was designed to test the hypothesis that interleukin-1 alpha (IL-1 alpha) and beta directly affect progesterone, and oestradiol production in cultures of purified human granulosa cells. Luteinized granulosa cells were obtained from women during in-vitro fertilization cycles. Granulosa cells with and without associated white blood cells were cultured in the presence of IL-1 alpha and IL-1 beta (0.5-50 ng/ml) for 48 h. Media were changed at 24 h intervals and assayed for progesterone and oestradiol. In separate experiments, granulosa cell viability was assessed with the tetrazolium salt reduction assay, haemocytometer cell counts, and Trypan blue dye exclusion. Our results indicate that progesterone synthesis by basal and human chorionic gonadotrophin (HCG)-stimulated granulosa cells co-cultured with white blood cells was inhibited by 5.0 ng/ml of IL-1 alpha and IL-1 beta at 48 h of culture. In the presence of white blood cells, granulosa cell oestradiol synthesis was inhibited by IL-1 beta but not IL-1 alpha. Oestradiol was inhibited after both 24 and 48 h of culture and was maximally affected by 5.0 ng/ml of IL-1 beta. In contrast, basal and HCG-stimulated oestradiol production by granulosa cells cultured free of white blood cells was inhibited only by IL-1 alpha. IL-1 alpha at 5.0 ng/ml produced maximal inhibition of basal oestradiol (57%) and HCG-stimulated oestradiol (41%) production at 48 h of culture. Gonadal steroid inhibition by IL-1 alpha and IL-1 beta was not mediated through cytotoxic or antiproliferative effects on granulosa cells. Specificity of the granulosa cell response to IL-1 alpha and IL-1 beta was demonstrated by abrogation of steroid inhibition with anti-IL-1 alpha and IL-1 beta neutralizing antibodies. In conclusion, IL-1 alpha directly inhibited the production of oestradiol by human ovarian granulosa cells. IL-1 alpha and IL-1 beta also exerted indirect effects on steroid production via white blood cells that are usually present in granulosa cell cultures if steps are not taken to remove them. These data support the hypothesis that cytokines play an important role in intra-ovarian regulation of steroid biosynthesis.

Influence of follicular phase duration on human granulosa-luteal cell subpopulations in natural and stimulated IVF-ET cycles

OBJECTIVES

To observe the granulosa-luteal cell subpopulations presented within follicular aspirates concerning duration of the follicular phase and the type of IVF protocol.

DESIGN

Cells were obtained from dominant follicles of 40 women with natural IVF-ET cycles, in which preovulatory hCG was given when the follicle was mature, and from 40 follicles of 32 women with hMG and hCG stimulated IVF-ET cycles. Granulosa-luteal cell subpopulations were observed by computerized image analysis in which hCG was localized using immunoperoxidase staining.

RESULTS

(1) The nonluteinized granulosa cells from natural developing follicles were larger than those from stimulated ones regardless of the follicular phase duration. (2) The size of each luteinized cell subpopulations was influenced neither by the two IVF protocols nor by the follicular phase duration. (3) The hCG stained cells from natural developing follicles were larger than the ones from stimulated follicles and their relative number in aspirates was higher. Cell areas and distribution were not influenced by the duration of follicular phase. (4) In stimulated conditions, hCG stained cells became larger if follicular phase was longer.

CONCLUSIONS

Duration of the follicular phase influences the immunocytochemical hCG localization and the morphometric characteristics of granulosa-luteal cell subpopulations presented within natural developing follicles and stimulated ones.

Activation of phospholipase D by prostaglandin F2 alpha in rat luteal cells and effects of inhibitors of arachidonic acid metabolism

In rat luteal cells labeled with [3H]oleic acid, PGF2 alpha-stimulated phospholipase D (PLD) activation was investigated. The PLD activity was detected by measuring the accumulation of [3H]phosphatidylethanol (PtdEt) in the presence of ethanol. PGF2 alpha stimulated PtdEt accumulation at concentrations of more than 100 nM in the presence of ethanol. However, PtdEt accumulation did not change in the absence of ethanol. PGF2 alpha (1 microM) increased PtdEt accumulation after 1 min, and the accumulation reached a plateau by 2-3 min. These results indicate that PGF2 alpha activates PLD in rat luteal cells. U-73122, a phospholipase C (PLC) inhibitor, and staurosporine, a protein kinase C (PKC) inhibitor, did not inhibit PGF2 alpha-stimulated [3H]PtdEt accumulation. These results suggest that PGF2 alpha-induced PLD activation is different from PLC-PKC systems. We reported previously that PGF2 alpha stimulated the release of arachidonic acid. The effects of indomethacin, nordihydroguaiaretic acid (NDGA), and 5,8,11,14-eicosatetraynoic acid (ETYA), inhibitors of arachidonic acid metabolism, on PGF2 alpha-stimulated PtdEt accumulation were examined. Pretreatment with indomethacin enhanced PGF2 alpha-induced PtdEt accumulation. In contrast, pretreatment with NDGA and ETYA inhibited PGF2 alpha-induced PtdEt accumulation. It is suggested that PGF2 alpha-stimulated PLD activation is mediated via lipoxygenase products.

Regulation of insulin-like growth factor-I and progesterone synthesis by insulin and growth hormone in the ovine ovary

Insulin-like growth factor-I (IGF-I) is an intraovarian regulator of follicular development in the rat, but it is uncertain how applicable this model is to other species. Ovine granulosa and luteal cells were cultured for 2 wk in defined medium to investigate the regulation of ovarian IGF-I synthesis. IGF-I was measured by RIA of concentrated media extract, and progesterone production was also assessed. In granulosa cell cultures from preovulatory follicles, IGF-I output was initially undetectable with the output rising from about Day 6, whereas midcycle luteal cells produced low concentrations of IGF-I throughout the culture period. In granulosa cells, insulin in the range of 0.1-10 micrograms/ml stimulated a dose-dependent increase in output per day of IGF-I and also caused IGF-I production to start at an earlier time in culture, but a lower dosage (10 ng/ml) consistently increased progesterone synthesis. High dosages of estradiol (10(-6) M) caused a small increase in IGF-I production whereas lower dosages had no effect. Growth hormone (GH) alone (10 ng/ml-10 micrograms/ml) did not stimulate either progesterone or IGF-I output. In the presence of insulin, GH caused a marked increase in progesterone but had no effect on IGF-I. These results suggest that IGF-I is not a major product of granulosa cells in the ewe, although there is low luteal production. Furthermore they indicate that the actions of the metabolic hormones insulin and GH on ovarian progesterone synthesis are probably mediated directly through their own receptors rather than through either ovarian IGF-I synthesis or the type 1 IGF receptor.

Endothelins inhibit FSH-mediated function via ETA receptors in cultured human granulosa-lutein cells

Endothelins (ETs) are a family of vasoactive peptides involved in granulosa and luteal cell function in some animal species. However, the potential relevance of ETs in ovarian physiology remains unclear, and the direct action of the peptides in the human ovary has not been studied to date. Experiments were conducted to determine whether ET-1 and ET-3 could regulate the follicle stimulating hormone (FSH)-induced cell response in human granulosa-lutein cells in culture. The FSH-mediated cell rounding process was used as an indicator of cell response, as previously described (Lawrence et al., 1979). Forskolin, cholera toxin, 8-Br-cyclic AMP, isobutylmethylxanthine (IBMX), rolipram and FSH all stimulated similar cell morphological changes, indicating that the cell rounding process was mediated by cyclic AMP. Although ET-1 and ET-3 alone failed to alter cell shape, the FSH-induced cell response was totally inhibited by treatment with ET-1 (10(-10) mol/l) and ET-3 (10(-7) mol/l). In addition, treatment of the cells with BQ123, an antagonist of ET binding on ETA receptor subtype, totally prevented the inhibitory effects of ET-1 and ET-3 on the FSH-induced response. The data presented here show that human granulosalutein cells are a site of ET reception and action. Endothelins inhibit cyclic AMP-dependent FSH-mediated function and the ET(A) receptor participates in this effect.