Metabolism of progesterone to estrogens and androgens by individual follicles of the goat ovary

Development of follicles in the goat ovary is characterized by the presence of four or more waves of follicular growth in the same cycle. Dominant follicle features also differ from the ones observed in other species. It has been previously shown that serum estrone (E1) is the predominant estrogen during puberty and continues being high in the adult female goat. Serum estradiol (E2) may be beyond the limit of sensitivity of RIA during puberty, but can be measured in the adult female. The objective of the present study was to investigate the steroid metabolism, focused on the androgens and estrogens synthesis, of the ovarian follicles of the goat. For this purpose follicles of different sizes (3-9 mm) were dissected from the ovaries of adult goats and separately dissociated in trypsin. Cells from each follicle were singly incubated in DMEM plus BSA and (3)H-progesterone. Some cells were exposed to hCG or FSH. At the end of the incubation period the media was obtained, ether-extracted and steroids separated by thin layer chromatography. The methodology used showed that follicular cells produced androgens (testosterone (T) and androstenedione (A4)), 17α-OHP4 and estrogens (estradiol-17β (E2) and estrone (E1)). Most follicles responded to hCG and FSH by increasing androgen and estrogen production. Some follicles produced mainly androgens suggesting they are evolving to atresia. E1/E2 ratio was related to the size of the follicle. E1 production was higher than E2 production in 3-6 mm follicles. The capacity to respond to FSH and hCG suggests the presence of FSH and hCG receptors in small antral follicles. In conclusion, the present results show that the follicular cells of the ovary metabolize progesterone to androgens and estrogens. Steroid metabolism studies showed that as it occurs in other mammals, follicles may undergo atresia at any stage of development. Estrone production was found in most follicles and was regulated by gonadotropins. Results show that at least, the Δ4 pathway is active in the ovarian follicles of the adult goat.