Uterine and peripheral blood concentrations of vasodilator prostaglandins in conscious pregnant rabbits.

The concentrations of prostaglandin E2 (PGE2) and prostacyclin (PGI2) were estimated in blood obtained from the uterine venous effluent and a peripheral artery of conscious pregnant and nonpregnant rabbits. The blood was analyzed both with a superfusion bioassay and radioimmunoassays. PGE2, but not PGI2, was detected in a very high concentration in the uterine venous effluent of the pregnant rabbit. The peripheral blood of pregnant animals also revealed increased levels of only PGE2. The results of both assay techniques correlated closely. These studies suggest that the uteroplacental unit is the source of the increased peripheral level of the potent vasodilator PGE2. In contrast, these data fail to support the notion that PGI2 is the primary systemic-acting vasodepressor prostaglandin in rabbit pregnancy.