Follicular Growth is Characterized by Biochemical Interplay of Proliferation and Apoptotic Death in Bovine Follicular Cells

Contents This study was conducted to characterize the degree of proliferation and atresia in mid‐luteal and follicular phase bovine follicles of different size containing morphologically good quality cumulus oocyte complexes. Follicular cell proliferation was estimated by enzyme immunoassay for tissue polypeptide specific antigen and atresia by an enzyme immunoassay for apoptosis. The relationship between follicular apoptosis and proliferation was inverse in the mid‐luteal stage ovaries, whereas in follicular stage ovaries the tissue polypeptide specific antigen was increased in follicles with the highest degree of apoptosis. Follicular stage follicles showed a higher degree of apoptosis in comparison with the mid‐luteal stage. This was caused by an increased apoptosis in follicles with less than 3 mm and greater than 5 mm diameter. In conclusion, the data indicate a sophisticated interplay between follicular growth and atresia in dependence of oestrous stage and follicular size.