Morphological and biochemical correlates of equine ovarian follicles as a function of their state of viability or atresia.
The histological features and hormonal content of follicular fluid of antral follicles during oestrus were correlated. As a result it was possible to characterize several categories of viable and atretic follicles. A seemingly important stage in maturation appeared to be at 3 cm in diameter since follicular oestrogens and androgens underwent a 3-fold increase in concentration at that size. Evidence was obtained to suggest that oestrogens are anti-atretogenic. However, a drop in oestrogens was not the cause of atresia since degeneration commenced when levels were high. Contrary to the concept that androgens are atretogenic in some species, it was also evident that elevated androgens did not precipitate spontaneous atresia. Theca epithelioid cells not only underwent histological luteinization in viable follicles as they matured toward ovulation but occasionally in atretic follicles as well. Elevated prostaglandin F levels were associated with follicles in the transitory states of either luteinization or atresia. Granulosa cells of viable follicles only were capable of specifically binding hCG. It was not determined whether loss of binding capacity or atresia occurred first. Follicular atresia in the mare appears to be a gradual process of which the initiating cause remains unknown.
D000728:Androgens / Q000378:metabolism; D000818:Animals; D006063:Chorionic Gonadotropin / Q000378:metabolism; D004967:Estrogens / Q000378:metabolism; D004971:Estrus; D005110:Extracellular Space / Q000502:physiology; D005260:Female; D006736:Horses / Q000502:physiology*; D006080:Ovarian Follicle / Q000166:cytology* / Q000502:physiology; D010060:Ovulation; D011247:Pregnancy; D011374:Progesterone / Q000378:metabolism; D011460:Prostaglandins F / Q000378:metabolism
D000728:Androgens; D006063:Chorionic Gonadotropin; D004967:Estrogens; D011460:Prostaglandins F; D011374:Progesterone