Estrogen-regulated uterine vascularization modulates the guinea pig intrauterine environment

The effects of experimentally-induced, uterine vascular restriction on uterine blood flow (UBF) and uterine blood volume (UBV) capacity, as well as the dependent intrauterine oxygen tension (IUpO2) measurements used as an indication of luminal nutrient availability, were examined using ovariectomized, estrogen (E)-treated guinea pigs. Following 3 days of E treatment, both UBF and UBV measurements were found to be elevated and associated with a causally-related increase in intraluminal uterine oxygen availability levels. Following the acute clamping of the uterine arteries, both UBF and UBV levels decreased dramatically and induced a rapid fall in associated intrauterine luminal oxygen tension measurements. As a result of chronic (i.e., 6 h) restriction of segmental blood flow to the uterus by vascular cauterization, both UBV and IUPO2 levels were suppressed as compared with sham-operated control levels, whereas UBF rates were not significantly altered. The results of the present studies are the first quantitative demonstration that either acute or chronic reductions in uterine vascular capacity or competency can induce rapid and dramatic changes in the intrauterine nutritional environment recognized to be essential for the initiation, support and maintenance of nidation and subsequent fetal-placental development.