OESTROGEN BIOSYNTHESIS BY SEGMENTS OF BOVINE FOLLICLE AND THE EFFECT OF FOLLICLE STIMULATING HORMONE PREPARATIONS

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Abstract
[4-14C] Testosterone was converted to [14C]estrone and [14c]170-estradiol on incubation with slices of bovine follicles. These metabolites were identified by sequential chromatography, derivative formation and re crystallization to constant 14c[beta]H ratio. Both Graafian and atretic follicles were able to synthesize these estrogens from testosterone. The yield of [14C]estrone plus [14c]17[beta]-estradiol, measured by reverse isotope dilution analysis, varied from 4 [mu][mu]moles to 4459 [mu][mu]umoles in the 19 follicles tested. Differences, much greater than the measured experimental error, were also found in the yields from the 2 halves of individual follicles. The difficulties imposed by these findings in demonstrating an effect of gonadotrophins are discussed. On incubation of segments of 2 follicles, identified histologically as Graafian follicles, in the presence of ovine follicle stimulating hormone, the yield of radioactive estrone and 17[beta]-estradiol from [4-14C]testosterone was markedly reduced. In 8 other follicles, the majority of which were atretic, the conversion of [4-14C]testosterone was not influenced by gonadotrophin in vitro. These results would suggest that, in some follicles, follicle stimulating hormone in vitro may modify steroid biosynthesis. In these cases the major locus of action of gonadotrophin on steroid biosynthesis appears to be before the synthesis of testosterone.