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.