ALTERATIONS IN CYTOSOLIC CA2+, MG2+, H+, NA+ AND K+ CONCENTRATIONS IN CULTURED-HEPATOCYTES DURING HYPOXIC CONDITIONS

Aim: It is assumed that disturbances of cellular ion homeostasis, especially an increase in the cytosolic Ca2+ concentration, are of decisive importance for hypoxic cell injury. The aim of this study is the determination of alterations in the cytosolic Ca2+, Mg2+, H+, Na+ und K+ concentration in cultured hepatocytes during hypoxia. Methods: The alterations of ion homeostasis under hypoxic conditions were studied in primary cultures of isolated rat hepatocyes by using fluorescence microscopy. Results: The measurements of cytosolic Ca2+ concentration showed no alterations during the first 3-4 h of hypoxia. About 1-2 h before cell injury became evident Ca2+ increased from 147 +/- 28 to 385 +/- 31 nM. Similarly the cytosolic Mg2+ concentration increased from 0.63 +/- 0.05 to 1.42 +/- 0.11 mM in a late stage of hypoxia. In contrast, the cytosolic Na+ concentration increased continuously from 16 +/- 2 mM at start to 76 +/- 9 mM after 5 h of hypoxic conditions. The cytosolic K+ concentration remained constant for 2 h (129 +/- 7 mM) but then decreased down to 31 +/- 18 mM. The intracellular H+ concentration increased slightly under hypoxic conditions, the pH decreased from 7.35 +/- 0.02 to 7.19 +/- 0.04. Conclusion: The results indicate that cytosolic Ca2+ plays only a minor role in the pathomechanism of hypoxic hepatocellular injury but suggest an important role of the cytosolic Na+ concentration in this process.