Effect of cadmium on acute-phase protein synthesis in perfused rat liver

The induction of alpha 1-acid glycoprotein by methylmercury

The incorporation of [14C]leucine into protein was measured in liver preparations and blood of rats following the s.c. administration of methylmercury hydroxide (24 mg/kg body wt) or turpentine (5.0 ml/kg body wt). The translatability of the RNA obtained from polysomes in an mRNA-dependent reticulocyte lysate was elevated significantly in the preparations derived from the treated rats compared to control rats. Immunoprecipitation of the labelled translation products or of serum proteins showed that the mRNA activity and the synthesis of alpha 1-acid glycoprotein, an acute phase reactant, was elevated by the methylmercury treatment as well as by the turpentine-induced inflammatory response.

Protective effect of metallothionein on cadmium toxicity in isolated rat hepatocytes

An isolated rat hepatocyte preparation was used to study the cellular toxicity of cadmium and the protective effects of metallothionein on cadmium-induced toxicity. Exposure of primary suspension cultures of isolated rat hepatocytes to Cd2+ (0-35.7 microM) for 15 min resulted in a dose-dependent reduction in the synthesis of cellular proteins during a subsequent 6 h incubation. Such inhibition could not be correlated with cellular lethality or gross membrane damage. Pre-induction of metallothionein in hepatocytes by zinc treatment in vivo of donor rats protected hepatocytes in vitro from cadmium-induced inhibition of protein synthesis. The protective effects in zinc-pre-induced hepatocytes are not due to alterations in the level of total cellular cadmium, but could be accounted for by the redistribution of intracellular cadmium in the presence of high levels of zinc-metallothionein. The data suggest that metallothionein exerts its protective effect by a kinetic detoxification mechanism, i.e. a decrease in reactive intracellular cadmium.

Effects of cadmium toxicity upon the in vivo and in vitro activity of proteins and five enzymes in blood serum and tissue homogenates of Mugil cephalus

This study reports changes in total protein and certain liver, heart, gill and serum enzymes after exposing fish or tissue homogenates and serum to Cd, i.e. in vivo and in vitro effects. Five enzymes were selected for assay; aspartate amino transferase (AAT), alanine amino transferase (A1AT), alkaline phosphatase (A1P), acid phosphatase (ACP) and lactic dehydrogenase (LDH). Total protein content in the exposed fish showed an increase in the liver, gill and serum while there was no change in heart protein. The sensitivity of the five assayed enzymes to Cd varied in different tissues. Gill AAT, A1AT were the most sensitive. Liver A1P and heart LDH showed the maximum inhibition at higher Cd concentrations.

Does lead exposure influence liver protein synthesis in rats?

The liver and serum of rats was studied 18 hr following the i.p. administration of 0.5 mg Pb2+/100 g body wt. The incorporation of [14C]leucine into proteins was measured in ribosomal and mRNA fractions incubated in vitro and was markedly stimulated in the Pb2+ treated rats. Similar results were found when the proteins of liver and serum were labelled by the injection in vivo of [14C]leucine. The increased mRNA activity appears to be chiefly for acid serum proteins of approx. Mr 44,000, 41,000, 33,000 and 18,000.

The effect of cadmium on kidney ribosomes

Rats received 2.6 mg/kg CdCl2 24 h prior to removing the kidneys and preparing the ribosomal fraction. The amount of ribosomal RNA was decreased 28% and there was a significant increase in bound ribosomes relative to free ribosomes following cadmium. The activity of these ribosomes from the kidney of cadmium-treated animals was nearly doubled either using endogenous mRNA or poly(U), together with elongation factors prepared from control rat liver. When ribosomal subunits were prepared and recombined in a cell-free assay system, the increased ribosomal activity was located in the 60S subunit. In chronic experiments for 2.5 or 11 weeks, cadmium chloride was administered in the drinking water at 100 or 250 ppm. The ribosomal RNA concentration was not decreased at 100 ppm for 2.5 weeks, yet the activity of the ribosomes was increased about 50%. AT 250 ppm for 2.5 weeks or 100 ppm for 11 weeks the ribosomal RNA concentration was decreased 15% and 7%, respectively, while the activity of the ribosomes was once more increased by about 50%. The increase in ribosomal activity after cadmium chloride are discussed in relation to the reported effects of cadmium chloride and of mercuric chloride on renal metallothionein and on renal tubules.