A Protective Function Against Radical Stress Mediated by the Intracellular Calcium in Rat Hepatocytes

The role of intracellular Ca2+ in CCl4 hepatotoxicity in rats was clarified by measuring detailed changes in serum ALT values and intracellular Ca2+ after CCl4 administration. Intracellular Ca2+ responded to CCl4 intoxication with a biphasic increase. The first intracellular Ca2+ peak increased up to 5.6-fold the control level at 1 hour, and the second Ca2+ peak 6.5-fold at 3.5 days. We further examined the effects of drugs on serum ALT activity and intracellular Ca2+ in rats administered at 1 hour prior to or 3 hours after CCl4 administration. The results showed that the first Ca2+ increase might be attributable to a signal arising from the extent of hepatic injury. The second Ca2+ increase might act to activate cellular protective functions. We discussed that sustained intracellular Ca2+ increases may be involved in autoprotection, namely susceptibility against a toxication.