Ultrastructural evidence for estradiol synthesis in the ovary of persistent-estrous rats exposed to continuous illumination.
The relation between sex hormone levels in blood and ultrastructural changes of ovarian follicles was examined in persistent-estrous rats exposed to continuous illumination (LL) for 100 days. Plasma LH showed a tonic level secretory pattern, and circulating estradiol and estrone concentrations were relatively high, while both levels of FSH and progesterone were low. Various stages of growing and degenerating follicles were observed in the ovary of the LL-exposed rats. The early stage of antral follicle did not seem to possess the ability of steroidogenesis. Theca cells around mature antral follicles contained prominent Golgi apparatuses, plenty of smooth endoplasmic reticulum (ER), abundant free ribosomes and many round-mitochondria. A few newly formed lipid droplets were seen in some of theca cells. Granulosa cells contained much distended rough ER, well-developed mitochondria, several lipid droplets and microfilaments. The theca cells of abnormal follicles with hyperplastic and infolded layers of granulosa cells contained many lipid droplets. However, the development of the smooth ER became hindered with increasing lipid droplets in the theca cell. On the other hand, granulosa cells of abnormal follicles contained greater numbers of lipid droplets than those of antral mature follicles, and were equipped with well-developed cytoplasmic organelles as were those of mature antral follicles. Theca interna cells of abnormal follicles may be more involved in the secretion of androgen, which has already been accumulated in the lipid droplets, than the cells involved in the active synthesis of the hormone, while the granulosa cells may convert its androgen to estrogen. The present findings suggest that both follicles of mature and abnormal types in the LL-exposed rat retain enough capacity of estradiol production and participate in the continued elevation of circulating estradiol, probably resulting in the stimulation of the theca cells by the tonic level of LH and of the granulosa cells by the levels of FSH, which are lower than the basal values during the normal 4-day estrous cycle.
D000818:Animals; D004958:Estradiol / Q000096:biosynthesis*; D004971:Estrus; D005260:Female; D012739:Gonadal Steroid Hormones / Q000097:blood; D008027:Light; D010048:Ovarian Cysts / Q000378:metabolism / Q000473:pathology; D006080:Ovarian Follicle / Q000648:ultrastructure; D010053:Ovary / Q000378:metabolism* / Q000648:ultrastructure; D051381:Rats; D011919:Rats, Inbred Strains; D012741:Sexual Maturation; D013997:Time Factors
D012739:Gonadal Steroid Hormones; D004958:Estradiol