Ovarian blood flow and oxygen transport to the follicle during the preovulatory period.

The mechanism of ovulation, especially the mechanism of follicle rupture, is still uncertain. Ovarian blood flow, ovarian vessel morphology and oxygen transport to follicle were therefore studied during the preovulatory period. Japanese white rabbits, weighing 3.0-4.4 kg, were used as the experimental animal. Ovulation was induced by the administration of PMS (100 iu, IM) and hCG (100 iu, IV). The ovulation was observed at 10-13 h after hCG administration. Continuous measurement of ovarian blood flow was facilitated by the crossed-thermocouple inserted into the unilateral ovary. The variation of ovarian blood flow was expressed as the percentage ratio based on the post-mortem value ( = 0%) and the initial value prior to hCG administration ( = 100%). Histologic changes of ovarian blood vessels were observed at intervals of every 2 hours after hCG administration. Oxygen transport to follicle was compared at 7 and 12 h after hCG administration. The ovarian blood flow increased rapidly within 1 h following hCG administration. High percentage increases were demonstrated during 2 h to 5 h, showing a peak value of 155.3 +/- 12.7% at 3 h. The ovarian blood flow decreased gradually from 5 h to 8 h and then was maintained at about 110% after 8 h. The perifollicular and stromal vasodilatations were confirmed at 2 h and moderate dilatation was observed during 4 h to 6 h. At 10 h, just prior to ovulation, vasodilatation became most remarkable especially at the apical vessels.(ABSTRACT TRUNCATED AT 250 WORDS)