Steroïd production by bovine follicles in vitro : influence of size , stage of cycle and culture system

Non-atretic bovine follicles of varying sizes and obtained at different stages of the oestrous cycle were cultured for 24 hrs, (1) on grids in a conventional static system, (2) in rolling tubes or (3) in a continuous flux system ; after culture steroids were determined in the culture media. For comparative purposes determinations were also made of the profile of steroids secreted into the follicular fluid by follicles in vivo. Small (2.0-5.0 mm in diameter) sized follicles in vivo secreted high levels of testosterone, lower amounts of progesterone and little amounts of cestradio)-17p into the follicular fluid. The profile of steroids secreted by this class of follicles in vitro depended upon the culture system used. In the static and rolling tube systems the small sized follicles secreted steroids in a pattern similar to that in the follicular fluid in vivo in this respect that testosterone is the main steroid secreted. An entirely different pattern, dominated by high cestradiol-17P levels, was produced when these follicles were cultured in the continuous flux system. Medium (5.1-8.0 mm in diameter) sized follicles in vivo secreted nearly equal amounts of the three steroids mentioned. Also in this class of follicles the steroid production in vitro