Na+/H+ exchange in porcine cerebral capillary endothelial cells is inhibited by a benzoylguanidine derivative.

Abstract Na + /H + exchange activity has been examined in endothelial cells isolated from porcine brain capillaries. Intracellular pH (pH i ) changes were monitored using a confocal laser scanning microscope and the pH-sensitive fluorescence indicator 2′,7′-bis-(2-car☐yethyl)-5,6-car☐yfluorescein (BCECF). Acid load of the brain capillary endothelial cells was performed with a NH 4 Cl (20 mM) prepulse. In bicarbonate-free solutions pH i recovered within 3 to 10 min. Removal of extracellular Na + ions demonstrated that H + extrusion after an acid load of the cells was Na + dependent. The Na + /H + exchange could be completely blocked by EIPA (5-(N-ethyl-N-isopropyl)amiloride) as well as by the novel inhibitor 3-methylsulfonyl-4-piperidinobenzoyl guanidine hydrochloride (HOE 694) in concentrations of 1 to 10 μM, respectively. EIPA and HOE 694 in a concentration of 0.1 μM caused a partial block of Na + /H + exchange.