The effect of LH/FSH, dibutyryl cyclic AMP, and prostaglandins on the production of estrogens by rabbit granulosa cells in vitro

Abstract

The purpose of this study was to establish the effects of trophic hormones on the production of estrogens by rabbit granulosa cells. A pure population of these cells was isolated from preovulatory follicles (1-15 mm in diameter) of estrous rabbits, and cultured for 6 days with either one or a combination of the following hormones: androstenedione, Pergonal (LH/FSH), dibutyryl cyclic AMP (Bu2cAMP), prostaglandin F2alpha (PGF2alpha), or prostaglandin E2 (PGE2). The medium was collected every 2 days and progesterone (P), estrone (E1) and estradiol-17 beta (E2beta) were measured by radioimmunoassay. Granulosa cells cultured as controls (i.e., without exogenous trophic hormones) secreted P spontaneously and its secretion was stimulated 100 to 1,000 fold with LH/FSH and Bu2cAMP, but not with PGF2alpha or PGE2. Androstenedione, either alone or with trophic hormones had no apparent effect on the cytology of the granulosa cells or their ability to secrete P. In the absence of exogenous androstenedione, the cultures produced very small amounts of E1 or E2beta (smaller than 100 pg/ml), either spontaneously or in response to LH/FSH, B12cAMP, PGF2alpha, or PGE2. Incubating granulosa cells with exogenous androstenedione (1 mug/ml) resulted in a 30- to 150-fold increase in E2beta production, which was stimulated an additional 3- to 5-fold with LH/FSH and Bu2cAMP, but not with PGF2alpha or PGE2. In most cultures, E2beta production was restricted to the first 2 days in vitro. Bu2cAMP, however, maintained E2beta production at relatively high levels throughout the duration of the experiment, but there was a progressive decrease in its production. The production of E1 was only 5 percent of E2beta, but the pattern of secretion was similar for both estrogens. These results suggest that cyclic AMP could have a role in regulating the synthesis of estrogens by rabbit granulosa cells.