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The aim of the study is to clarify the role of the kinin forming system on ovulation. The results were as follows, Plasma prekallikrein of superovulated prepubertal rats was decreased to 50-60% of the normal level after PMS injection and 80-90% of the normal level after hCG injection. The lowest level was 33.8% 39 hours after PMS injection. Aprotinin suppressed the superovulation of prepubertal rats at doses of 16.7 X 10(4) KIE and 37.8 X 10(4) KIE (p less than 0.01). These results showed that the kinin production system has an effect on ovulation. As the sex steroid hormone, estradil benzoate, progesterone and testosterone propinate were used in oophorectomized mice. They had no effect on the plasma prekallikrein level. The plasma prekallikrein level during the estrus cycle of mature female mice was 85.5% of the control level in preestrus, 80.3% in estrus, 83.7% in metestrus and 89.8% in diestrus. The mean was 83.9%, which was significantly lower than that for oophorectomized mice (94.1%). It is proved that plasma prekallikrein was consumed and the kinin forming system was accelerated in the ovary with ovulation.

The effects of removal of the olfactory bulbs on the estrous cycle and the weight of reproductive organs were examined in mice of the IVCS, ICR and C57BL/6 strains. Sham-operated and intact mice served as controls. Virgin female mice were surgically deprived of the olfactory bulbs at 8 weeks of age and caged individually in air-conditioned rooms with controlled lighting (14 hours of light, from 5 a. m. to 7 p. m., each day). Vaginal smears were observed daily. The animals were killed and their principal organs weighed at 6 weeks after the operation. The results obtained were as follows; 1) The olfactory bulb ablation prolonged the length of estrous cycle of mice of the ICR (6.0 days) and C57BL/6 (5.0 days) strains, but did not modify the cycle in those of the IVCS strain (4.0 days). 2) A decrease of ovarian weights by this operation was observed in the mice of the IVCS and ICR strains, but not C57BL/6 strain.

The author, in an attempt to investigate the mechanism of ovulation, conducted studies on ovarian blood flow hemodynamically and ovarian vessels histologically during ovulation induced by FSH and LH in rabbits. Continuous measurement of ovarian blood flow was facilitated by the crossed-thermocouple inserted into the unilateral ovary relatively close to its cortex. Histological changes of the ovarian blood vessels were observed every two hours and 13 h after LH administration. (1) The ovarian blood flow showed a rapid increase as 116.6 +/- 4.3% (M +/- S.E) at 15 min, 122.1 +/- 5.1% at 30 min following LH administration and maintained its high level percentage during the subsequent 2 h to 4 h, showing the peak with 156.2 +/- 9.1%. The ovarian blood flow showed a gradual decrease after 4 h. (2) A dilatation was observed in the perifollicular and stromal vessels from 2 h. The vessels maintained a considerable dilatation during 4 h to 8 h and the most conspicuous vasodilatation was manifested, especially at the apical vessels, at 10 to 13 h just prior to ovulation. Although the wall of the apical vessels was remarkably thin at that time, the overswelled apical vessels remained until ovulation. The ovulation was not seen without the rupture of the apical perifollicular vessels. These hemodynamic and histological results suggest a congestion in ovarian blood vessels during the ovulatory period. Such blood congestion presumably plays a significant role in the mechanism leading to ovulation.