Cardiac output and genital blood flow distribution during the preovulatory period in rabbits.

Cardiac output and blood flow distribution to the genital organs of rabbits was studied using radioactive microspheres for a period of 9 h following HCG administration. Throughout this period the ovarian blood flow was higher (1.2 ± 0.3 mI/mm/organ) than in the estrous animal (0.17 ± 0.02). The maximal ovarian blood flow occurred 4 h after HCG, and was associated with high perfusion rate (12 ± 3 ml/min/g). The cardiac output increased from 276 ± 62 mI/mm in estrus animals to 479 ± 82 following HCG, with a peak value of 780 ± 133 at 4 h. The fractional distribution of the cardiac output to the oviducts (0.18 ± 0.02 percent); uterus (0.40 ± 0.06 percent); brain, (1 percent); and kidney (21 percent) did not change during the preovulatory period. The fraction of cardiac output distributed to the ovaries increased from 0.10 ± 0.3 percent in estrus, to a maximum of 0.43 ± 0.06 percent at 4 h. The differences in the vascular response of the genital organs suggest the existence of local regulatory mechanisms which may play a role in the mechanisms leading to ovulation.