Incerpi S, Spagnuolo S, Terenzi F, Leoni S
Department of Cellular and Developmental Biology, University of Rome, Italy.
Am J Physiol. 1996 Mar;270(3 Pt 1):C841-7. doi: 10.1152/ajpcell.1996.270.3.C841.
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.
在无HCO₃⁻的名义溶液中，研究了表皮生长因子（EGF）对胎鼠和成年大鼠肝细胞中Na⁺/H⁺逆向转运体的调节作用。使用荧光pH敏感细胞内探针2',7'-双（羧乙基）-5（6）-羧基荧光素（BCECF）测量，EGF（10 nM）使成年大鼠肝细胞中的逆向转运体活性比基础值激活了0.22±0.03（平均值±标准差；n = 10）个pH单位。EGF的作用被氨氯地平类似物5-（N-乙基-N-异丙基）氨氯地平（EIPA）、Na⁺泵抑制剂哇巴因以及EGF受体酪氨酸激酶活性抑制剂埃布他汀类似物所抑制。EGF对成年大鼠肝细胞中Na⁺/H⁺逆向转运体的作用似乎是由蛋白激酶C（PKC）和G蛋白系统介导的。在20天和22天的胎肝细胞中，未观察到EGF和PKC激活剂佛波酯12-肉豆蔻酸酯13-乙酸酯对Na⁺/H⁺逆向转运体的影响。逆向转运体对高浓度氨氯地平和EIPA的不同敏感性表明，与成年细胞相比，胎肝细胞中可能表达了不同数量的Na⁺/H⁺逆向转运体单位或不同的亚型。
