RELATIONSHIP BETWEEN PROGESTERONE AND ESTRADIOL CONTENTS OF FOLLICULAR-FLUID AND THE MORPHOLOGICAL APPEARANCE OF GRANULOSA-CELLS OF FOLLICLES COEXISTING WITH CORPORA-LUTEA IN BOVINE OVARIES

Bovine ovaries (n=149) bearing follicles (>5 mm) coexisting with matur e corpora lutea (CL;>10 mm) were obtained at a local abattoir without regard for the reproductive status of the donor cows. Most corpora lut ea were 21 to 25 mm in diameter, and nearly half of the largest follic les were 11 to 15 mm in diameter. When oocytes were aspirated from fol licles 16 to 30 mm in diameter, approximately 60% of them proved to be degenerated. Concentrations of progesterone (P4) and estradiol-17 bet a (E2) in the follicular fluid of 23 follicles (>10 mm) were determine d. Progesterone and estradiol-17 beta were found to be the major hormo ne in 16 (69.6%) and 7 (30.4%) of the follicles, respectively. Light-m icroscope observations of the granulosa cells of the same 23 follicles showed that 7 were deficient in mural granulosa cells, and that 15 of the remaining 16 follicles were atretic or luteinizing. Ultrastructur al observations of granulosa cells revealed many lipid droplets in the cytoplasm of follicles coexisting with mature CL, suggesting the init iation of luteinization. These results show that approximately 70% of the follicles were P4-dominant and that more than 95% of them were mor phologically degenerated. Thus it is suggested that morphological sign s of atresia precede changes in the concentrations of hormones in the follicular fluid of follicles coexisting with corpora lutea (>10 mm) d uring the middle of the estrous cycle.