Cytosolic pH regulation in perfused rat liver: role of intracellular bicarbonate production

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• 作者：Vidal ; Giovanni ; Durand ; Thierry ; Canioni ; Paul ; Gallis ; Jean-Louis
• 关键词：Cytosolic pH ; Nuclear magnetic resonance ; Endogenous bicarbonate ; (Rat liver) ; DIDS ; 4 ; 4&prime ; -diisothiocyano-2 ; 2&prime ; -disulfonic acid stilbene ; [H⁺]_input ; proton concentration of perfusate reaching the liver ; [H⁺]
• 刊名：Biochimica et Biophysica Acta (BBA)/General Subjects
• 出版年：1998
• 出版时间：September 16, 1998
• 年：1998
• 卷：1425
• 期：1
• 页码：224-234
• 全文大小：261 K

文摘

The contribution of metabolic bicarbonate to cytosolic pH (pH_cyto) regulation was studied on isolated perfused rat liver using phosphorus-31 NMR spectroscopy. Removal of external HCO⁻₃ decreased proton efflux from 18.6±5.0 to 1.64±0.29 μmol/min per g liver wet weight (w.w.) and pH_cyto from 7.17±0.06 to 6.87±0.06. In the nominal absence of bicarbonate, inhibition of carbonic anhydrase by acetazolamide induced a further decrease of proton efflux of 0.69±0.26 μmol/min per g liver w.w. reflecting a reduction in metabolic CO₂ hydration, and hence a decrease of H⁺ and HCO⁻₃ supplies. Even though 27 % of the proton efflux was amiloride-sensitive under bicarbonate-free conditions, amiloride did not change pH_cyto, revealing the contribution of additional regulatory processes. Indeed, pH regulation was affected by the combined use of 4-acetamido-4′-isothiocyanostilbene-2,2′-disulfonic acid (SITS) and amiloride since pH_cyto decreased by 0.16±0.05 and proton efflux by 0.60±0.14 μmol/min per g liver w.w. The data suggest that amiloride-sensitive or SITS-sensitive transport activities could achieve, by themselves, pH_cyto regulation. The involvement of two mechanisms, most likely Na⁺/H⁺ antiport and Na⁺:HCO⁻₃ symport, was confirmed in the whole organ under intracellular and extracellular acidosis. The evidence of Na-dependent transport of HCO⁻₃ in the absence of exogenous bicarbonate implies that the amount of metabolic bicarbonate is sufficient to effectively participate to pH_cyto regulation.