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 folli cles (greater than or equal to 3 mm in diameter) in cattle after induc tion of luteolysis with the PGF(2 alpha) analogue luprostiol. Special attention was paid to the presence of atypical granulosa cells in thes e follicles to obtain additional data to help evaluate the hypothesis that these cells are markers of follicular atresia. Animals were injec ted 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 prostag landin-induced luteolysis, the mean number of medium-sized and large n onatretic follicles and of medium-sized atretic follicles had not chan ged in heifers and in cows, compared with those of untreated animals. However, in heifers, contrary to cows, the development of a preovulato ry-sized follicle was initially accompanied by an increase in the numb er of large definitely atretic follicles. Atypical granulosa cells can be considered as markers for a lower quality follicle, on the basis o f 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 granul osa cells will grow to preovulatory size, growth of this follicle with in 2 days after prostaglandin treatment was almost 9 mm and over 10 mm in heifers and cows, respectively. In cows, most growth of follicles was observed at the first day after prostaglandin treatment; in heifer s, this occurred one day later.