RELAXIN INDUCES OVULATIONS IN THE IN-VITRO PERFUSED RAT OVARY

The effects of human recombinant relaxin on ovulation and ovarian ster oidogenesis were investigated in vitro using a perfused rat ovary mode l. Ovaries of equine chorionic gonadotrophin (ECG; 20 IU)-primed Sprag ue - Dawley rats were perfused for 21 h. Ovarian release of oestradiol and progesterone was measured during the perfusion period and the num ber of ovulations was estimated by counting the released oocytes at te rmination of the experiment. Non-treated control ovaries did not ovula te whereas addition of ovine luteinizing hormone (LH; 100 ng/ml) resul ted in a mean (+/-SEM) number of ovulations of 3.0 +/- 0.8 from all tr eated ovaries. Relaxin (10 mug/ml) induced mean (+/-SEM) number of ovu lations at 2.4 +/- 0.2 in all treated ovaries but did not further incr ease the ovulation rate when combined with LH (mean +/- SEM 3.2 +/- 0. 4). AH ovulated oocytes in the groups stimulated by LH showed signs of nuclear maturation (germinal vesicle breakdown) when harvested, in co ntrast to ovulated oocytes in the relaxin group, which were immature ( presence of germinal vesicle). Progesterone and oestradiol release was significantly increased in the LH-stimulated groups but not in the gr oup treated only with relaxin, in comparison to the untreated control group. These results demonstrate that relaxin may have a paracrine rol e within the ovary and may facilitate ovulation, possibly by promoting connective tissue remodelling of the follicle wall.