erbstatin and ethylisopropylamiloride

The modulation by epidermal growth factor (EGF) of the Na+/H+ antiport in fetal and adult rat hepatocytes was studied in nominally HCO3- free solution. EGF (10 nM) activated the antiport in adult rat hepatocytes by 0.22 +/- 0.03 (mean +/- SD;n=10) pH units over basal value, measured with the fluorescent pH-sensitive intracellular probe, 2',7'-bis(carboxyethyl)-5(6)- carboxyfluorescein (BCECF). The effect of EGF was inhibited by amiloride analogue 5-(N-ethyl-N-isopropyl) amiloride (EIPA), by ouabain, inhibitor of the Na+ pump, and by erbstatin analogue, an inhibitor of the tyrosine kinase activity of the EGF receptor. The effect of EGF on Na+/H+ antiport in adult rat hepatocytes appeared to be mediated by both protein kinase C (PKC) and G protein system. No effect of EGF and phorbol 12-myristate 13-acetate, an activator of PKC, on the Na+/H+ antiport was observed in fetal hepatocytes of 20 and 22 days. A different sensitivity of the antiport to high concentrations of amiloride and EIPA suggests that altered amount of the Na+/H+ antiport units or different isoforms could be expressed in fetal compared with adult cells.

Topics: 4,4'-Diisothiocyanostilbene-2,2'-Disulfonic Acid; Amiloride; Animals; Cells, Cultured; Enzyme Inhibitors; Epidermal Growth Factor; Fetus; Fluoresceins; Fluorescent Dyes; GTP-Binding Proteins; Hydroquinones; Kinetics; Liver; Ouabain; Protein Kinase C; Protein-Tyrosine Kinases; Rats; Rats, Wistar; Sodium-Hydrogen Exchangers; Tetradecanoylphorbol Acetate