Bradykinin potentiates LH-induced follicular rupture in the rat ovary perfused in vitro.

The possible role of bradykinin as a modulator of LH-induced ovulation was investigated using a model of the in-vitro perfused rat ovary. Ovaries from immature rats, primed with pregnant mare's serum gonadotrophin (PMSG; 20 IU), were perfused in vitro for 20 h, starting on the morning of induced proestrus. Stimulation in vitro with luteinizing hormone (LH; 0.1 microgram/ml) resulted in 3.4 +/- 1.2 ovulations per treated ovary, whereas no ovulations occurred in the unstimulated group. Bradykinin (5 microM) added to the perfusion system at 0, 2.5, 5, 7.5 and 10 h gave two ovulations in one ovulating ovary out of five ovaries perfused. When LH was combined with bradykinin, added to concentrations of 1 microM and 5 microM at the above-mentioned five time points, the numbers of ovulations were 12.2 +/- 2.7 and 15.6 +/- 3.7 per treated ovary, respectively. Bradykinin (5 microM), administered as a single dose concomitantly with LH, resulted in no further increase in the ovulation rate (3.6 +/- 1.6). Bradykinin did not affect cyclic AMP or steroid release from unstimulated or LH-stimulated ovaries. These data indicate a role of bradykinin in the ovulatory process of the rat, potentiating LH-induced ovulations.