Effects of repeated dose administration of lead and zinc ions on protein synthesis in mouse liver

The present study was devoted to examine 14 days effects of lead and/or zinc ions on translation machinery of laboratory mice. Material and methods: 4 – 6 weeks old white outbreed mice received intraperitoneal injections of Pb(CH3COO)2 solution (10 mg Pb per kg of body mass) and/or ZnSO4 solution (1.56 mg Zn per kg of body mass) for 14 days. Control animals received injection of the same volume of saline. Liver cell-free translation system was made on the basis of supernatant. Translation rate and level were evaluated by the incorporation of radioactive amino acids into newly synthesized protein and peptides. Total tRNAs were isolated using deproteinized extract of liver tissue. Postmitochondrial supernatant was used as a source of seryl-tRNA synthetase (SRS). Activities of tRNASer and SRS were measured by an aminoacylation reaction using 14C-labeled serine. Metallotioneins (MT) was assayed in mice liver by the colorimetric method with DTNB (Ellman’s reagent). Results: After 14 days exposure of mice to Pb(CH3COO)2 solution the rate and the level of translation in mice liver decreased by 47% and 34%, respectively. Two weeks of exposure to ZnSO4 solution decreased these parameters by 24% and 16%, respectively. Mice pre-treatment with Zn2+ did not show any protective role to either the rate nor to the level of translation in mice liver. It was determined that activity of mice liver SRS after 2 weeks intoxication with Pb2+ has increased by 55%. Pretreatment of mice with Zn2+ attenuated the effect of Pb on SRS activity after 14 days of administration. The acceptor activity of tRNASer isolated from liver of all three metal treated mice groups (Pb, Zn, Zn+Pb) after 14 days of administration, decreased by 45%, 55% and 60%, respectively. Two weeks of exposure to Pb2+ as well as Zn2+ increased the content of MT in liver of all three metal treated groups of mice (Pb, Zn, Zn+Pb) by 55%, 25% and 25%, respectively. [...].