Right and Left Ventricular Cultured Endocardial Endothelium Produces Prostacyclin and PGE₂

The endothelium profoundly affects subjacent vascular smooth muscle function. An analogous relationship between endothelial endocardial cells (EEC) and the myocardium is suggested by Brutsaert et al.'s observation that EEC modulate the contractility of subjacent myocardium [1]. Prostanoids are a major product by which vascular endothelium affects smooth muscle, but similar prostanoid production by EEC has not been described. To determine whether both right and left ventricular EEC produce prostacyclin (PGI₂) and prostaglandin E₂ (PGE₂), ovine EEC were cultured. EEC prostanoid production was measured under basal conditions and after stimulation with arachidonic acid or calcium ionophore A23187. EEC from both ventricles demonstrated sustained prostacyclin and PGE₂ production. Prostacyclin production was 10 times greater than PGE₂. These results suggest that endocardial prostanoid production could act both locally, to modulate platelet and myocardial function, and distally, on downstream vascular tone.