The Influence of Constrictor Drugs on the Distensibility of the Splanchnic Venous System, Analyzed on the Basis of an Aortic Model

Abstract

The distensibility of the aorta was measured in anesthetized dogs by injecting blood at controlled rates into an isolated segment. Constrictor drugs produce a moderate increase in distensibility of the aorta at low pressure ranges and a more marked increase in distensibility at normal pressures. Studies of the splanchnic venous system of intestinal loops by the same method, and also by a method which does not require interruption in blood flow, gave evidence of the same type of distensibility phenomena as seen in the aorta, although at low pressures the venous distensibility tends to be actually decreased by vasoconstriction. The splanchnic venous system also differs from the aorta in that it is very dependent upon the rate of pressure-volume change. These results are analyzed in terms of the basic mechanisms involved and their physiologic implications.