Pregnancy- and gender-related changes in pulmonary vascular reactivity

Pregnancy is a state of altered pulmonary vascular reactivity, but the conclusions about changes in reactivity have varied with the agents or species chosen for study. The present study was designed as a comprehensive analysis of pregnancy-induced and gender-related differences in pulmonary vascular reactivity in one species. Using an isolated perfused feline lung preparation, the pulmonary vascular responses to angiotensin II, serotonin, histamine, epinephrine, norepinephrine, and acute hypoxia (FIO2, 8%) were compared between males, females, and pregnant females. Vascular reactivity (maximum response) and drug sensitivity (ED50) were compared using cumulative dose-response data for each pharmacological agent. The results demonstrate that (1) reactivity to angiotensin II, serotonin, epinephrine, and acute hypoxia is decreased during pregnancy, while the response to norepinephrine remain unchanged, (2) drug sensitivity is unchanged with serotonin and the catecholamines, increased with histamine, and decreased with angiotensin II, and (3) the responses to acute hypoxia and histamine have significant gender-related differences in reactivity independent of the changes observed during pregnancy.