A comparison of histological and non-histological indices of atresia and follicular function.

Histological indices of atresia for bovine follicles greater than or equal to 5 mm in diameter were compared with potential non-histological indices of atresia such as opaqueness of the exposed surface of non-excised follicles, concentrations of steroids in follicular fluid (FF) and specific binding of gonadotropins by granulosal cells. Each non-excised follicle was classified as clear (n=86), intermediate (n=79), or opaque (n=115), on the basis of the appearance of its exposed surface. A section of tissue from each follicle was evaluated histologically for atresia and assigned to one of the following categories: non-atretic, intermediately atretic, strongly atretic, or luteinized-atretic. Concentrations of estradiol (E), progesterone (P), and testosterone (T) and capacity of granulosal cells to bind radioactive ovine follicle-stimulating hormone (oFSH) and human chorionic gonadotropin (hCG) were determined for each follicle. Overall incidence of atresia was similar for clear (n=66%), intermediate (60%), and opaque (72%) follicles. Opaque follicles, however, were more likely to be strongly atretic (42%) than were clear (21%) or intermediate (23%) follicles. Non-atretic and intermediately atretic follicles had similar concentrations of E, P, and T and similar capacities to bind gonadotropins. Strongly atretic and luteinized-atretic follicles contained a higher concentration of P, lower E, and a reduced capacity of granulosal cells to bind oFSH than non-atretic and intermediately atretic follicles. A ratio of P:E in FF greater than or equal to 10 usually (greater than 90%) indicated that a follicle was atretic. However, lesser ratios of P:E did not accurately indicate whether follicles were atretic.(ABSTRACT TRUNCATED AT 250 WORDS)