Oxytocin in human follicular fluid and its possible role in the ovulatory process as studied in vitro

Oxytocin immunoreactivity was determined in follicular fluid from human follicles at different stages of development. The concentration of oxytocin was highest in pre-ovulatory follicles. The measured oxytocin was found to co-elute with synthetic oxytocin in an h.p.l.c. system. The influence of oxytocin on the incorporation of [3H]proline into isolated human follicular wall was studied in vitro. Oxytocin induced a decrease of radiolabelling in both unripe and pre-ovulatory follicles, indicating an inhibitory effect on collagen synthesis. This effect of oxytocin was not affected by indomethacin. An oxytocin analogue, 1-deamino-2-D-Tyr(OEt)-4-Thr-8-Orn-vasotocin, did not inhibit the incorporation of [3H]proline. The pre-ovulatory augmentation of oxytocin concentration in follicular fluid might reflect a physiological role for oxytocin in the ovulatory process. This assumption is strengthened by the observation that oxytocin may influence follicular collagen metabolism in vitro and by this means participate in the regulation of follicular rupture in the human.