In-vitro steroid secretion of tertiary atretic bovine follicles in a superfusion system correlated to their histological features.

In monotocus mammals most of the tertiary follicles are atretic. The experimental design of a blind study was used to evaluate the steroid secretion pattern and histological features of atretic bovine follicles. Steroidogenesis of the vesicles was studied with the aid of a superfusion system, and the superfused follicles were evaluated independently using the histological classification elaborated by Marion et al. Twelve single atretic follicles removed during the follicular and luteal phases of twelve cows were superfused for 10 h and then histologically processed. Follicles in early and definite contracting atresia secreted predominantly testosterone, whereas follicles in definite cystic, advanced contracting and late atresia secreted predominantly progesterone. Such secretion was independent of the stage of the oestrus cycle of the animal, so that follicles with the same histological pattern had a characteristic steroid secretion pattern, which was not influenced by the stage of the oestrus cycle at the time of follicular removal. In conclusion, atretic follicles should be considered significant endocrine organs.