Cardionatrin causes vasodilation in vitro which is not dependent on the presence of endothelial cells.

Vasodilation, in vitro, evoked by atrial extracts (cardionatrin) was compared with the relaxation due to acetylcholine and papaverine in rat precontracted aortae with and without endothelium. Ventricular extracts were tested as controls. Atrial extracts and papaverine caused a similar concentration-dependent relaxation of both preparations whereas acetylcholine failed to relax preparations without endothelium. Ventricular extracts were ineffective on both preparations. It is concluded that the response of the preparations to atrial extracts (cardionatrin) is not dependent on the presence of the endothelial cells. Some pathophysiological implications are discussed.