EFFECTS OF INTRA-ARTERIAL OUABAIN ON MESENTERIC AND CAROTID HEMODYNAMICS

¹ Departments of Physiology and Biophysics and Surgery, University of Oklahoma Medical Center, Oklahoma City, Oklahoma

Ouabain is a mesenteric precapillary constrictor. The purpose of this study was to determine by direct measurements of mesenteric hemodynamics whether this effect represents a local pharmacologic action on the mesenteric circulation. Mesenteric blood flow was measured in anesthetized dogs with an electromagnetic blood flowmeter, arterial and portal pressures were measured with strain-gauge transducers and mesenteric vascular resistance was calculated from these measurements. In each experiment ouabain was infused i.a. at progressively increasing rates from 5 to 80 µg/ min for five-minute periods. At all infusion rates mesenteric blood flow decreased significantly and resistance increased. These responses were elicited even at low doses which did not alter heart rate or arterial or portal pressures. Similar experiments were conducted on the common carotid artery of the dog, with similar results; i.a. infusion of ouabain evoked a constrictor response with a decrease in blood flow. Our findings indicate that ouabain is a local constrictor of the precapillary segment of the peripheral circulation. Its use is questioned in patients whose mesenteric blood flow has already been reduced, as in shock.