Effect of ovarian hormones on the uterine vascular bed

Abstract

Left uterine artery blood flow (UBF) was monitored in oophorectomized ewes during administration of ovarian hormones. After oophorectomy, UBF decreased to barely recordable levels. A single injection or daily injections of estradiol increased UBF markedly for one to 2 days. Thereafter, flow progressively decreased after the single injection or decreased and then stabilized at rates significantly below the peak rates during daily injections. Alone, progesterone had no significant effect on UBF. When superimposed on daily estradiol, progesterone decreased UBF about 30 per cent. Following progesterone withdrawal, UBF increased markedly in a pattern similar to that observed after the initial administration of estradiol. These findings indicate that estradiol causes marked uterine vasodilatation. During prolonged estradiol administration, resistance develops to this effect. While progesterone may cause some uterine vasoconstriction, its principal action would seem to be a sensitization of the vascular bed to the effect of estradiol. Left uterine artery blood flow (UBF) was monitored in oophorectomized ewes during administration of ovarian hormones. After oophorectomy, UBF decreased to barely recordable levels. A single injection or daily injections of estradiol increased UBF markedly for one to 2 days. Thereafter, flow progressively decreased after the single injection or decreased and then stabilized at rates significantly below the peak rates during daily injections. Alone, progesterone had no significant effect on UBF. When superimposed on daily estradiol, progesterone decreased UBF about 30 per cent. Following progesterone withdrawal, UBF increased markedly in a pattern similar to that observed after the initial administration of estradiol. These findings indicate that estradiol causes marked uterine vasodilatation. During prolonged estradiol administration, resistance develops to this effect. While progesterone may cause some uterine vasoconstriction, its principal action would seem to be a sensitization of the vascular bed to the effect of estradiol.