Micromorphology of antral follicles in cattle after prostaglandin-induced luteolysis, with particular reference to atypical granulosa cells.

Dutch Friesian heifers (n = 13) and cows (n = 13) were used to obtain information about the number, size and micromorphology of antral follicles (> or = 3 mm in diameter) in cattle after induction of luteolysis with the PGF2 alpha analogue luprostiol. Special attention was paid to the presence of atypical granulosa cells in these follicles to obtain additional data to help evaluate the hypothesis that these cells are markers of follicular atresia. Animals were injected i.m. with 15 mg of the synthetic prostaglandin on day 10 or day 11 of the oestrous cycle. The ovaries were collected on day 12, that is 48 and 24 h after injection of luprostiol, respectively. After prostaglandin-induced luteolysis, the mean number of medium-sized and large nonatretic follicles and of medium-sized atretic follicles had not changed in heifers and in cows, compared with those of untreated animals. However, in heifers, contrary to cows, the development of a preovulatory-sized follicle was initially accompanied by an increase in the number of large definitely atretic follicles. Atypical granulosa cells can be considered as markers for a lower quality follicle, on the basis of their absence in preovulatory-sized follicles and their presence in large numbers in a high proportion of definitely atretic follicles. If it is assumed that only a nonatretic follicle without atypical granulosa cells will grow to preovulatory size, growth of this follicle within 2 days after prostaglandin treatment was almost 9 mm and over 10 mm in heifers and cows, respectively.(ABSTRACT TRUNCATED AT 250 WORDS)