Hormonal and cellular interactions in follicular steroid biosynthesis by the sheep ovary

Armstrong, D.T.; Weiss, T.J.; Selstam, G.; Seamark, R.F.

Journal of Reproduction and Fertility. Supplement 30: 143-154

1981


ISSN/ISBN: 0449-3087
PMID: 6300384
Document Number: 173804
The cAMP production by granulosa cells from the smallest follicles studied (1-3 mm diameter) was stimulated by FSH but not by HCG in in vitro cultures; this suggested that functional FSH receptors exist at this early stage of differentiation. Medium-sized follicles (4-6 mm) responded to both FSH and HCG. Granulosa cells were unable to synthesise androgens, but readily converted exogenous testosterone to oestradiol-17 beta . This conversion occurred to a limited extent in the cells from the smallest follicles, but was much greater in medium and large (>6 mm) follicles. Oestradiol production by theca preparations from small follicles was barely detectable, but increased markedly with increasing follicle size. Androgen (androstenedione and testosterone) production by theca preparations was stimulated by HCG. This stimulation was short-lived, and levels declined to below control values after 6 h of culture. This decline could not be prevented by addition of cAMP. The presence of granulosa cells with thecal preparations (i.e. follicle wall tissue) enhanced production of androgen by the theca, the effect being more marked for testosterone than for androstenedione. In vivo studies in which granulosa cells and follicular fluid were removed during the preovulatory period suggested that granulosa cells and/or follicular fluid contributed to the oestradiol secreted into the ovarian vein during this period, but did not exclude a significant contribution by the theca as well.

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