Coronary vasodilation by fatty acids.

Fatty acids increase the coronary flow rate of rat hearts, perfused according to the Langendorff technique. Long-chain and medium-chain fatty acids are more effective vasodilators than short-chain fatty acids. The vasodilatation by fatty acids does not proceed through the intermediate formation of the vasodilator adenosine, nor by stimulation of adenylcyclase activity. Since at low Ca2+ concentrations fatty acids not only stimulate the coronary flow rate but also cardiac contractility, it is suggested that especially the lipophilic fatty acids have calcium ionophoric properties leading to increased Ca2+ removal from smooth muscle cytosol and hence to vasodilatation. Preliminary experiments, moreover, indicate that both medium- and long-chain fatty acids, like prostaglandin E1 and Ca2+, inhibit membrane ATPase(s) of aorta smooth muscle cells, suggesting increased Ca2+ binding to vascular smooth muscle cell membranes.