The conscious instrumented rabbit: a model for the study of mechanisms of blood pressure regulation during pregnancy.

Conscious pregnant and nonpregnant rabbits were used to further evaluate the role of prostaglandin (PG) and plasma renin activity (PRA) in the systemic hemodynamics of pregnancy. Pregnant rabbits had high peripheral blood levels of both PGE2 and PRA. Systemic blood pressure was not affected in either pregnant or nonpregnant by the administration of an inhibitor of prostaglandin synthesis. Pregnant rabbits, however, had a much larger decrease in blood pressure than nonpregnant animals when given the angiotensin I (AI)-converting-enzyme inhibitor, captopril. Pregnant rabbits were more resistant to the pressor effect of exogenous AII than nonpregnant animals. The pressor effect of AII increased in pregnant rabbits after the administration of meclofenamate and parturition but was not changed by volume expansion. In contrast, the sensitivity of nonpregnant rabbits to AII increased after volume expansion, but not after treatment with inhibitors of prostaglandin synthesis. These studies demonstrate that a remarkable similarity exists between pregnant rabbits and pregnant women in the pressor response to AII. This study is the first to correlate the vasopressor response to AII with PRA and the level of a circulating vasopressor prostaglandin in pregnant animals. The results strongly suggest that this model will be fruitful in further attempts to define the factors controlling systemic hemodynamics during pregnancy.