Acid and alkaline phosphatase in bovine antral follicles

Acid and alkaline phosphatases were measured in the follicular fluid of 766 individual follicles from 96 cows. Follicles were obtained by bilateral ovariectomy or at slaughter from animals at various stages of the estrous cycle and pregnancy. Mean follicle size varied with the physiological state of the cow (P less than .0001). Acid phosphatase activity (U/microliters) varied inversely with follicle size (P less than .001) but not with stage of the estrous cycle or gestation. Total acid phosphatase activity per follicle increased with follicle size (P less than .05). Neither acid phosphatase nor alkaline phosphatase concentration was associated with atresia. Alkaline phosphatase activity (U/microliters) was greater in the smallest follicles (less than 50 microliters) than in other size groups (P less than .0001). Alkaline phosphatase activity (U/microliters) was greater (P less than .05) during the preovulatory phase of the estrous cycle than during other phases. A high concentration of follicular fluid phosphatases cannot be used as a marker for atresia but is characteristic of healthy small antral follicles.