Blood flow in the reproductive organs of the mouse after hypophysectomy, after gonadotrophin treatment, during the oestrous cycle and during early pregnancy.

Abstract

SUMMARY The indicator fractionation technique was examined and found to be of value in the measurement of organ blood flow in the anaesthetized female mouse with [131I]iodoantipyrine as the indicator substance. Blood flow per unit weight of the brain and ovary was shown to decline rapidly after hypophysectomy. A single injection of pregnant mare serum gonadotrophin (PMS), given 4 days after hypophysectomy, restored the blood flow of these organs to normal levels. Uterine blood flow was unaffected by hypophysectomy, and was significantly increased by PMS injection. Significant changes in brain, ovarian and uterine blood flow were observed during the oestrous cycle, early pregnancy and in mice induced to ovulate by injections of gonadotrophin. There was a tendency for brain and ovarian blood flow to decline before ovulation. By contrast, significant transient increases in blood flow to the brain and ovary were observed on day 3 of pregnancy. It is thought that these changes are related to the mechanisms which initiate implantation. Uterine blood flow was lowest in mated and unmated mice on the day of oestrus and rose to peak levels 2 days later. In pregnancy, however, peak uterine blood flow was recorded between days 3 and 4 and was higher than at any stage in the oestrous cycle. Although it tended to fall after day 3, uterine blood flow in pregnancy did not decline again to low levels as it did in the oestrous cycle. The possible physiological significance of the results is discussed, and the limitations to their interpretation are considered.