PREVENTIVE EFFECT OF PRETREATMENT WITH LOW DOSE OF METALS ON THE ACUTE TOXICITY OF METALS IN MICE

Abstract

In a previous short communication, it was reported that mice injected with small amounts of metals tolerated the lethal dosage of the same metals given 24 hs later. The present study was designed to obtain the precise information on the tolerance to the acute toxicity of various kinds of metals. This tolerance was determined by the difference of mortality between the mice given the lethal doses of metals with and without pretreatment.From the results of this experiment, it was found that metals were divided into 3 groups as follows :Group I: Metals with which the mortality caused by challenge are reduced with pretreatment. These metals which can develop a tolerance against their own toxic action are Ag, As, Cd, Hg, In, Pb, Mn, and Sn.Group II : Metals with which their pretreatment had no effect on mortality caused by challenging are Cu, Ni, Se, and Tl.Group III: Metals with which pretreatment increased their mortality and these metals became more toxic by pretreatment : Ba, Cr, Fe, and Zn.From these results, it can be concluded that pretreated mice show a tolerance to the toxic action of most of contaminant metals and do not to that of essential metals.Moreover, it was found that metals belonging to Group I have the ability to develop a cross-tolerance while those of Group II and III do not.