Endothelin-1 signaling is altered in cardiac cells from deoxycorticosterone acetate-salt hypertensive rats

The cardiac cellular effects of endothelin-1 (ET-1) on intracellular free Ca2+ concentration ([Ca2+]i) were investigated in deoxycorticosterone acetate (DOCA)-salt rats with severe cardiac hypertrophy. [Ca2+]i was measured by fura-2 methodology in ventricular cardiomyocytes and fibroblasts of DOCA-salt hypertensive and control unilaterally nephrectomized rats (Uni-Nx). Blood pressure and heart weight were increased (p < 0.01) in DOCA-salt rats compared to control rats. ET-1 (10(-12)-10(-6) M) increased [Ca2+]i in a dose-dependent manner in both cell types from control and hypertensive rats. However, ET-1-induced [Ca2+]i responses were significantly attenuated (p < 0.01) in cardiomyocytes and fibroblasts of DOCA-salt rats. Sarafotoxin S6c (S6c) increased [Ca2+]i in fibroblasts but not in cardiomyocytes. In conclusion, ET-1 dose-dependently increased [Ca2+]i in cardiomyocytes (primarily via ETA receptors) and fibroblasts (via ETA and ETB receptors). Cardiac cell ET-1 signaling pathways are blunted in DOCA-salt hypertensive rats. ET-1 may not play a critical role in the pathophysiology of the severe concentric cardiac hypertrophy present in DOCA-salt hypertensive rats.