Regulation of intracellular pH in isolated periportal and perivenular rat hepatocytes

Abstract

Background: Liver acinus shows a well-known metabolic zonation. The aim of this study was to investigate intracellular pH (pH1) regulation in isolated periportal (PP) and perivenular (PV) rat hepatocytes. Methods: 2,7-bis(carboxyethyl)-5(6)-carboxy-fluorescein was used as pH-sensitive dye. Hepatocyte subconfluent monolayers were acid-loaded by exposure to 20 mmol/L NH4Cl and alkali-loaded by reducing external CO2 and HCO3− at an external pH of 7.4. Results: In the presence of HCO3−/CO2, (1) baseline pH1 was higher in PP (7.25 ± 0.018) than in PV hepatocytes (7.20 ± 0.013) (P < 0.05); (2) pH1 recovery from an acid load was 40% higher in PP than in PV hepatocytes (P < 0.02) and was inhibited by amiloride by 36% in PV and 7% in PP hepatocytes; (3) DIDS inhibited amiloride-independent pH1 recovery from an acid load by 65% in PP and 52% in PV cells. In the absence of HCO3−/CO2, baseline pH1 and pH1 recovery from an acid load were not significantly different in PP and PV hepatocytes. pH1 recovery from an alkali load was 30% higher in PV than in PP cells (P < 0.02). Conclusions: Our data suggest that isolated PP rat hepatocytes show higher activity for Na+-HCO3− cotransport, whereas PV cells show greater activity for Cl−/HCO3− exchanger.