INTERACTION OF OVARIAN TISSUES IN THE CONTROL OF FOLLICULAR STEROIDOGENESIS IN CULTURE

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Abstract
The interaction between developing antral follicles and other ovarian tissues in sheep was examined in vitro. Small follicles (2·0–2·9 mm 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 180·4 ± 12·6 (s.e.m.) pmol mg tissue−1 24 h−1; oestrogen (61·7 ± 8·2 pmol mg−1 24 h−1) and testosterone (84·4 ± 9·2 pmol mg−1 24 h−1) accounted for 81% of the steroid secreted by control follicles. The presence of stromal tissue during co-culture depressed (P < 0·01) the subsequent output 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 < 0·01) 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.