Interaction of ovarian tissues in the control of follicular steroidogenesis in culture

The interaction between developing antral follicles and other ovarian tissues in sheep was examined in vitro. Small follicles (2\m=.\0\p=n-\2\m=.\9mm in diameter) were co-cultured with a single ovarian component for 48 h, then separated and cultured singly for a further 72 h during which time changes in follicular steroidogenesis and structure were measured. Control follicles, cultured together for 48 h before separation, had a mean total daily steroid output during the 72 h test period of 180\m=.\4 \m=+- \ 12\m=.\6(s.e.m.) pmol mg tissue\m=-\124 h\m=-\1; oestrogen (61\m=.\7\m=+-\8\m=.\2pmol mg\m=-\124 h\m=-\1) and testosterone (84\m=.\4\m=+-\9\m=.\2pmol mg\m=-\124 h\m=-\1) accounted for 81 % of the steroid secreted by control follicles. The presence of stromal tissue during co-culture depressed (P < 0\m=.\01)the subsequent out-put of total steroid by 22%, oestrogen by 81 % and testosterone by 38%; progesterone output was, however, over twice that of the controls. There were no distinctive structural differences between follicles in the control and stromal groups. Luteal tissue enhanced (P < 0\m=.\01)the output of total steroid by 51%, testosterone by 55% and progesterone by 242%; oestrogen output was similar to that in the controls. Follicles co-cultured with luteal tissue were characterized by extensive hypertrophy of the theca interna. Developing follicles co-cultured with large non-atretic follicles had a similar total steroid output, a slightly higher oestrogen output and more thecal hypertrophy than the controls. Follicles co-cultured with large atretic follicles differed from controls only with respect to their greater capacity to synthesize progesterone