COMPARISON BETWEEN ENDOCARDIAL AND GREAT VESSEL ENDOTHELIAL-CELLS - MORPHOLOGY, GROWTH, AND PROSTAGLANDIN RELEASE

The release of vasoactive mediators by vascular (VEC) and endocardial endothelial cells (EEC) has not been directly compared. In this study, in vitro morphological and cell growth characteristics and the rate o f prostanoid release were compared in cultured sheep endothelial cells from great vessels (VEC; pulmonary artery and aorta) and endocardium (EEC; right and left ventricles) harvested from the same animals. Morp hologically, in flasks, VEC demonstrated the classic cobblestone patte rn, whereas EEC developed numerous cytoplasmic interdigitations and ov erlaps. Rate of cell proliferation was greater for EEC than for VEC (P < 0.05): doubling time was shorter for EEC (34 +/- 3 h) than for VEC (45 +/- 5 h). Under static (no-flow) conditions, in response to arachi donic acid and calcium ionophore A-23187, the rate of prostacyclin (PG I(2)) and prostaglandin E(2) release by VEC and EEC was not different. In contrast, in response to flow and acute hypoxia (O-2 tension = 35 Torr), the rate of PGI(2) release was greater in EEC than in VEC (P < 0.0001). After 2 h of perfusion, the rate of PGI(2) release was 19-fol d greater for EEC than for VEC during normoxia and 34-fold greater dur ing hypoxia. Thus our study showed anatomic site of origin-dependent h eterogeneity in prostanoid release between VEC and EEC. Endocardial en dothelium is a greater source of PGI(2) than great vessel endothelium; in vivo, endocardial endothelial PGI(2) may inhibit local platelet ag gregation and modulate downstream vascular tone.