Capillary blood flow in the genital tracts of conscious ewes: cyclic changes and the effect of ovarian hormones.

The indicator fractionation technique with [86Rb]rubidium chloride as the indicator was used in conscious animals to determine the relative blood flow (RBF) as a measure of capillary blood flow in regions of the genital tract of cyclic ewes and of hormonally treated ovariectomized ewes. The RBF values in the ampulla, isthmus, uterus and cervix of cyclic ewes were markedly raised at pro-oestrus and declined thereafter to low levels during the remainder of the oestrous cycle. On Day 4 a small secondary rise in flow occurred in the ampulla and isthmus. In ovariectomized ewes, oestradiol induced high levels of RBF in the ampulla, isthmus, uterus and cervix whether the animals had been treated previously with progesterone or given concurrent small doses of progesterone. Though progesterone given alone caused a significant rise in RBF in the uterus, this effect appeared to be one occurring only during active re-growth of regressed tracts. The findings are discussed in relation to oestradiol inducing a stimulatory effect on RBF in the genital tract of the ewe around oestrus but not at Days 3-4 of the oestrous cycle.