Ouabain and responses to endothelium‐dependent vasodilators in the human forearm.

Abstract

Ouabain inhibits endothelium‐dependent vascular relaxation in vitro, but has not been studied in this regard in vivo. We have therefore measured blood flow responses to carbachol, bradykinin and sodium nitroprusside (endothelium‐dependent and endothelium‐independent vasodilators) infused into the brachial artery with and without co‐ infusion of ouabain (2 micrograms min‐1). Six healthy male volunteers were each studied on two occasions. Ouabain reduced basal forearm blood flow, by 18.0 +/‐ 4.1% (mean +/‐ s.e. mean, 2P less than 0.05), but had no significant effect on responses to any of the three vasodilators. These results indicate that effects of ouabain on endothelium‐dependent relaxation in vitro must be interpreted with caution. 1991 The British Pharmacological Society