Pharmacological actions of synthetic atrial natriuretic factor on coronary vascular smooth muscle

The pharmacological activities of synthetic atrial natriuretic factor (ANF) on cat coronary artery were studied in vitro. In the preparation of isolated cat coronary artery perfused at a constant flow, ANF (3-300 nM) decreased perfusion pressure in a concentration dependent manner, indicating coronary vasodilating activity. ANF also relaxed feline coronary strips when contracted by U-46,619, CTA2, angiotensin II, serotonin, leukotriene C4 and D4. This relaxant effect was independent in the presence of endothelial cells and occurred in the presence of guanylate cyclase inhibitor, methylene blue. ANF had no direct effect on electrically driven isolated cat papillary muscles signifying a lack of direct inotropic activity. It can be concluded that ANF may potentiate coronary vasodilation and therefore contribute to coronary regulation, without directly altering myocardial performance.