Effects of histamine, 5 hydroxytryptamine and epinephrine on pulmonary hemodynamics with particular reference to arterial and venous segment resistances.

Abstract

Studies were made of the effects of histamine and 5 hydroxytryptamine (5HT) on arterial and venous segmental resistances in the isolated perfused dog lung. The lung was perfused at constant flow while pressures were measured in the pulmonary artery (PA), left atrium (PV) and in either the pulmonary artery wedge position (PAw) or a small pulmonary vein (PVs). Arterial resistance changes were inferred from changes in the PA-PAw pressure drop, and venous resistance from the PAw-PV pressure gradient. Changes in lung weight were recorded continuously. It was found that histamine usually caused a greater increase of the venous resistance than of the arterial resistance, while 5HT usually increased the arterial resistance more than the venous resistance. When the predominant resistance increase was arterial the lung weight fell, but when there was a sizeable increase of the venous resistance the lung weight rose, presumably as a result of increased capillary blood content. The correlation coefficient between the change in lung weight and the change in venous resistance was + .791. Small pulmonary vein pressures rose after administration of epinephrine, norepinephrine, histamine and 5HT. This result gives further proof of constriction of pulmonary veins by these agents.