Angiotensin II stimulates the Na+/H+ exchanger in human umbilical vein endothelial cells via AT1 receptor

Angiotensin II (Ang II) has an important role in cardiovascular regulation and in the control of electrolyte balance, and its role in the regulation of Na+ transcellular movements through its actions on the activity of Na+/K+ ATPase is well documented. We showed previously that human umbilical vein endothelial cells (HUVEC) express the Ang II type 1 (AT1) receptor, which mediates Ang II modulation of Na+/K+ ATPase activity (1). We here investigate the effects of Ang II on the activity of the Na+/H+ exchanger in HUVEC. When compared with controls, incubation of HUVEC for 20 min with different concentrations of Ang II provoked significant increases in Na+/H+ activity. The stimulation was dose dependent between 1 and 10 nM Ang II and varied with time of incubation up to 20 min. The maximal response, obtained with 10 nM Ang II after 20 min treatment, resulted in a 65% increment in Na+/H+ activity. Preincubation of HUVEC with 10 microM DuP753 blocked Na+/H+ activation by Ang II. These results suggest that the effects of Ang II on both the Na+/K+ ATPase and the Na+/H+ exchanger may increase the transendothelial flux of Na+ and are mediated by the AT1 receptor.