Hormone secretion by monolayer cultures of human luteal cells

Relaxin in the marmoset monkey: secretion pattern in the ovarian cycle and early pregnancy

Relaxin is a peptide hormone with a broad range of biological activities, related not only to parturition and lactation but possibly also to decidualization, implantation, and early pregnancy. The present study was designed to investigate the secretion pattern of relaxin throughout the cycle and early pregnancy in the common marmoset monkey in relation to ovarian function and the systemic hormone milieu. First, a novel relaxin ELISA was developed and validated to confirm the pattern of relaxin secretion during pregnancy. Secondly, serum relaxin profiles were determined through nonconceptive and conceptive cycles and analyzed in relation to the concentration of other hormones and to the development of ovarian follicles and corpora lutea (CL). Blood samples were collected 2-3 times per week from the experimental animals and analyzed for relaxin, progesterone, and LH. The animals from the conceptive cycles were also ultrascanned at these time points to determine the ovarian status up to Day 25 of pregnancy. During early pregnancy, the relaxin levels in serum were approximately 1 ng/ml, increasing up to 15 ng/ml in the second trimester, at a time when progesterone levels had declined. In the third trimester, when progesterone levels were increasing again, the levels of relaxin decreased, returning to basal levels by term of pregnancy. In early pregnancy there was a parallel increase in both relaxin and LH/hCG, with the relaxin rise in the conceptive cycle appearing sooner than in the nonconceptive cycle, suggesting that, like chorionic gonadotropin (CG), relaxin may be a useful and early marker for pregnancy. Unlike the situation in the human, there was no correlation between the levels of either hormone and the number of CL detected, infants born, mother's age, or parity. Relaxin levels increased in early pregnancy before bioactive LH/CG, implying that relaxin is not directly regulated by this gonadotropin. Furthermore, hCG applied to nonconceptive females during the expected time of implantation caused an increase in progesterone but not in relaxin concentrations. In summary, the results obtained indicate that relaxin may be a reliable indicator of early pregnancy status in the common marmoset, but it is independent of direct CG influence.

Direct effect of gonadotropins on decidualization of human endometrial stroma cells

Decidualization of stromal cells isolated from proliferative human endometrium was achieved by adding to the culture medium human gonadotropins (FSH, FSH + LH, hCG). In addition to changes in the morphology of the stromal cells to the decidual phenotype, decidualization was evident from the expression of prolactin (PRL), demonstrated immunocytochemically, by Western blotting analysis, and by measuring its output into the medium through solid phase enzyme immunoassay. Gonadotropins also induced cAMP formation in the endometrial stromal cells under the same experimental conditions. This finding suggests that the mechanism by which gonadotropins promote decidualization of human endometrial stromal cells in vitro involves the introduction of cAMP, a compound that we have found to elicit the expression of PRL in this system. PRL is likely to be a key intermediate in the process of decidualization since it is by itself capable of inducing differentiation of the endometrial stromal cells to the decidual phenotype. Awareness of direct actions of gonadotropins on the endometrial cells and, in particular, of the decidualizing effects of FSH (Metrodin), FSH+LH (Pergonal) and hCG may contribute to the understanding of physiologic as well as pathophysiologic conditions relevant to endometrial functions and fertility.

Hormone release by primary amniotic fluid cell cultures

Amniotic fluid cells have been widely used in prenatal diagnosis; however, there is great heterogeneity of the cells and their origin. In this study we analyze the karyotype and release of human chorionic gonadotropin (hCG), human chorionic somatomammotropin (hCS), free estriol (E 3), prolactin (PRL) and progesterone (P) of amniotic fluid cells from primary cultures of six normal and two anencephalic fetuses. In all the amniotic fluid samples there was release of hCG; in one amniotic fluid, in which several tetraploid colonies were found. PRL and P were also released. The heterogeneity of amniotic fluid cell morphology and their hormone release in culture was confirmed. The presence of hormones like hCG supports the trophoblastic origin of some amniotic fluid cells from normal and anencephalic fetuses. Other hormones, such as PRL and P could be used in the differential diagnosis between the karyotype of fetal membranes and the true fetal karyotype. Amniotic fluid cell cultures used in prenatal diagnosis yielded second trimester placental cells without any elaborate methods that could be used as cell models for hormone studies.

Progesterone and relaxin secretion in relation to the ultrastructure of human luteal cells in culture: effects of human chorionic gonadotropin

This report describes the first study to correlate the ultrastructure of long-term monolayer cultures of human luteal cells with their secretion of relaxin and progesterone under basal and human chorionic gonadotropin-stimulated conditions. In culture from 14 to 28 days, cells from both corpora lutea of the menstrual cycle and corpora lutea of pregnancy took on characteristics of granulosa luteal cells, particularly after exposure to human chorionic gonadotropin. Relaxin was detectable in the luteal cell cultures only at early time points. The effect of human chorionic gonadotropin on media relaxin levels differed in cells of the cycle and cells of pregnancy. In the cells of the cycle, relaxin was detectable only on day 2 and was decreased by human chorionic gonadotropin (p less than 0.01). In cells of pregnancy, relaxin was detectable for the first 4 days of culture and was not affected by human chorionic gonadotropin. Progesterone was detectable in all the luteal cell cultures and was enhanced by human chorionic gonadotropin (10 and 50 IU/ml) after 24 days of exposure. At earlier time points in both the luteal cells of the cycle and the luteal cells of pregnancy, the human chorionic gonadotropin-induced increases in progesterone levels were not as consistent. However, in all cases of progesterone enhancement, smooth-surfaced endoplasmic reticulum was increased in the human chorionic gonadotropin-treated cells compared with corresponding controls, consistent with more active steroid production. In addition, gap junctions, considered to be responsive to trophic hormones, were increased in the treated cells. In conclusion, this long-term monolayer culture of human luteal cells, as monitored by ultrastructural and hormonal changes, retained the differentiated function of progesterone secretion and exhibited responsiveness to human chorionic gonadotropin. Therefore, morphologic and functional aspects of progesterone secretion may be investigated more closely with use of this long-term luteal cell culture system.

Progesterone secretion by primary cultures of rat luteal cells

Primary cultures were prepared from ovaries of immature rats that had been superovulated. The dispersed luteal cells attached to growth surfaces, formed monolayers and secreted progesterone. Progesterone accumulation in the medium was most pronounced in the first week of culturing. Removal of serum from the medium resulted in a progressive decline in progesterone concentration in the culture medium which reached basal levels by 5 hours. In medium without serum, the addition of hCG, FSH or prolactin stimulated an increase in progesterone secretion within 1 hour. Also cholera toxin stimulated a significant increase in progesterone levels in the medium. Prior exposure of cultures to estradiol for 3 days did not augment the response to hCG and inhibited the ability of cholera toxin to stimulate progesterone secretion. These results indicate that the steroidogenic function of rat luteal cells can be studied in culture and that a number of hormones rapidly stimulate the secretion of progesterone from these cells.

Immunoreactive beta-endorphin in sheep ovary

Although the ovarian production of sex steroids is of obvious physiological importance, recent studies suggest that peptides such as oxytocin, relaxin and inhibin are also synthesized in the ovary. We report here the presence of immunoreactive (ir) beta-endorphin, ir-adrenocorticotropic hormone (ACTH) and presumptive high molecular weight forms of both in extracts of sheep ovary, consistent with ovarian production from a common precursor. Our findings suggest that beta-endorphin and ACTH are produced and secreted by the follicular cells, and that their production may be related to the oestrous cycle.

Effects of serum and lipoproteins on steroidogenesis in cultured bovine luteal cells

The effects of serum and lipoproteins on the function of bovine luteal cells in tissue culture were examined. Corpora lutea from regularly cycling dairy cows were dissociated with collagenase and cultured in Ham's F-12 medium with or without serum. The serum-free medium was supplemented with insulin, transferrin and hydrocortisone. Addition of LH to the serum-containing medium did not increase progesterone (P4) production. When the luteal cells were cultured in serum-free medium. LH produced a dose-dependent increase (P less than 0.001) in P4 production during the first 24 h of culture. The responsiveness of the cells to LH then gradually declined, and remained low until days 9-11 of culture, at which time the cells regained their ability to respond to LH. The luteal cells were responsive to dibutyryl cAMP in both serum-containing and serum-free medium. Serum lipoproteins (low and high density) were able to produce a 150-260% increase in progesterone production by the luteal cells cultured in serum-free medium. The results indicate that the presence of serum in the cell culture medium inhibits the responsiveness of luteal cells to LH at a step prior to the increase in cellular cAMP, and that serum lipoproteins can be used to increase progesterone production by cultured bovine luteal cells.