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

Na+/H+ exchange activity has been examined in endothelial cells isolated from porcine brain capillaries. Intracellular pH (pHi) changes were monitored using a confocal laser scanning microscope and the pH-sensitive fluorescence indicator 2',7'-bis-(2-carboxyethyl)-5,6-carboxyfluorescein (BCECF). Acid load of the brain capillary endothelial cells was performed with a NH4Cl (20 mM) prepulse. In bicarbonate-free solutions pHi 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 microM, respectively. EIPA and HOE 694 in a concentration of 0.1 microM caused a partial block of Na+/H+ exchange.