Differential sensitivity of integrity criteria as indicators of cadmium-induced cell damage

The reliability of the stainability by Trypan Blue (TB) to detect membrane damage in hepatocyte suspensions of different TB stainability and in freshly isolated cells exposed to 50 microM cadmium (Cd) for 60 min was assessed by comparison with the leakage of lactate dehydrogenase (LDH) and NADH-oxidation. The cellular nitrophenyl-phosphate (NPP) uptake and the digitonin-induced fluorescence of 8-anilinonaphthalene-sulfonate-1 (dig-ANS-F) were introduced as integrity parameters of hepatocytes and compared with TB stainability. Cd was without effect on all these parameters. LDH-leakage was a poor criterion, whereas NADH-oxidation and dig-ANS-F were as sensitive as TB stainability. The NPP-uptake was more sensitive than TB stainability to indicate toxic Cd-effects when the plasma membrane still seemed to be intact. Because of the enhanced extracellular NPP-degradation, which resulted from the release of alkaline phosphatase, NPP-uptake was useful as a measure of Cd-induced damage only under certain conditions. These results confirm TB stainability as a simple and reliable criterion for plasma membrane integrity and therefore viability of hepatocytes also in Cd-toxicity.