Influence of cadmium, zinc and selenite ions on protein synthesis in mouse liver

摘要

The study aimed at evaluating short-term (24 h) in vivo effects of cadmium (Cd~(2+)), zinc(Zn~(2+)), and selenite ions (SeO_3~(2-)) on translational machinery in mouse liver. Activities oftranslation, tRNA~(Leu)and leucyl-tRNA synthetase (LRSase) were analysed by incorporations of [~(14)C] C]-labeled leucine ([~(14)C] -Leu) into specific products using liver preparations from mice after intraperitoneal (i.p.) injection of single doses of the following salts solutions: (1) CdCl_2(1.6 mg Cd per 1 kg of body mass); (2) ZnSO_4(3.1 mg Zn per 1 kg of body mass); (3) Zn-SO_4and after 20 min CdCl_2(amounts of respective elements indicated above); (4)Na_2SeO_3(1.25 mg Se per 1 kg of body mass); (5) Na_2SeO_3and after 20 min CdCl_2(amounts of respec-tive elements indicated before). In respect to control, time-dependent biphasic response oftranslation in the liver was determined following mice i.p. treatment with CdCl_2: diminu-tion by 38% at 2 h followed by a 51% increase at 8 h and by a 32% decrease at 24 h. NeitherZn~(2+) nor SeO_3~(2-) caused remarkable alterations of translation activity when liver had beenexposed to those ions for 2 h and 24 h. As compared to the control, Zn~(2+) and SeO_3~(2-) activatedtranslation in mice liver by 67% and by 26% respectively in the 8-h period of exposure. Pre-treatment with Zn~(2+) favoured the resistance of the translation system to Cd~(2+) only at 2 h,while pre-treatment with SeO_3~2favoured such a resistance at 2 h and at 24 h of Cd intoxica-tion. The acceptor activity of tRNA~(Leu)daecreased by 44-74% and the activity of LRSase by20-30% within a 24-h period following i.p. injection of CdCl_2.An exposure time-depend-ent decrease of tRNA~(Leu)acceptor activity versus an exposure time-dependent increase ofLRSase activity were observed in the preparations from ZnSO_4-injected mouse liver. Micepre-treatment with ZnSO_4prevented activity of LRSase within 24 h against Cd-induced in-hibition, but failed in the protection of the acceptor activity of tRNA~(Leu). Responses of thosetranslational components to SeO_3~(2-) were converse and biphasic: the maximum decreas-ing tRNA~(Leu)acceptor activity (by 66%) a with simultaneous and insignificant increase ofLRSase activity (by 12%), observed after 8 h, were followed by re-activation of tRNA andan insignificant decrease of LRSase activity after 24 h of liver exposure to Na_2SeO_3. In liverpreparations from SeO_3~(2-) and Cd~(2+) co-treated mice, Cd inhibitory effects on tRNA~(Leu)werealmost abolished within a 24-h period, whilst these effects manifested on LRSase at 2 h andwere partly relieved at 8 and 24 h following the treatment.