[Intracellular Ca2+ mediating biodefense signal on CCl4-induced autoprotection]

To study a role of intracellular Ca2+ on protection effects in animals against intoxication, that is, autoprotection. When carbon tetrachloride (CCl4) of 0.2 ml/kg was i.p. administered daily to male Donryu rats, the serum alanine aminotransferase (ALT) activity rose to a maximal level one day later, and then decreased to the control level within three days. Thus, the animals were not received any intoxication effect of CCl4 due to second, third and fourth administrations. Thus, animals have a sensitive and non-sensitive periods against intoxication of CCl4. In non-sense period, the animals were protective against the poison. Such protection is an autoprotection. To study a role of intracellular Ca2+ on CCl4-induced autoprotection, we measured the intracellular Ca2+ in hepatocytes isolated from rats after daily CCl4 i.p. administration. Then, the peaks of the intracellular Ca2+ centered on three days and twelve hours after the first CCl4 administration from the first to fourth administration. These results show that the peak of the intracellular Ca2+ is perfectly corresponding with the trough of the serum ALT; that is, the protective period in animals against intoxication. Therefore, this result means that intracellular Ca2+ can mediate biodefense signal caused by CCl4 intoxication.