Flow cytometric analysis of the effects of tri-n-butyltin chloride on cytosolic free calcium and thiol levels in isolated rainbow trout hepatocytes.

The toxic effects of tri-n-butyltin chloride (TBT) were investigated on isolated trout hepatocytes by flow cytometry (FCM). We developed a procedure permitting the study of cytosolic free calcium in these cells using the new fluorescent probe Fura Red. In parallel, changes in thiol levels upon exposure to TBT were also followed by FCM with the probe 5-chloromethylfluorescein-diacetate. Cell viability was monitored through FCM analysis using propidium iodide. Treatment of hepatocytes with TBT caused a time- and concentration-dependent loss of viability. The results show that TBT induced a sustained elevation of cytosolic free calcium in isolated trout hepatocytes before loss of viability was detectable. Data for the viable cells remaining after incubation with TBT were selected after appropriate gating with the flow cytometer. When this was performed, the data revealed that changes in cytosolic free calcium were not dependent upon TBT concentration and duration of exposure. Moreover, TBT induced a rapid and important depletion of thiols in cells which survived TBT exposure. The present results suggest that alterations in calcium homeostasis and intracellular thiols are involved in the mechanism of trout hepatocyte injury by TBT. FCM is a powerful tool to study metabolic disturbances caused by toxic agents on cells at an individual level.