Comparison of the toxicity and tissue distribution of cadmium in newborn and adult rats after repeated administration

Abstract

Male rats, 4 days or 7 weeks of age, were given seven sc injections of either saline (2 ml/kg) or 2 or 3 mg Cd/kg once every other day. Twelve to sixteen hours after the last injection, the animals were sacrificed and renal function was determined by measuring the in vitro uptake of p-aminohippurate by renal cortical slices, the plasma levels of creatinine and urea nitrogen, and the urinary excretion of glucose and protein. In addition, the morphology of various tissues was examined by light microscopy. The renal function tests mentioned above did not show any difference between the saline- and cadmium-treated rats at either age. However, histopathologically there was minor renal damage in the young adult rats treated with 3 mg Cd/kg. In the young adult rats treated with 2 mg Cd/kg and in the newborn rats treated with either doses of cadmium, there was no difference in the histopathology of the kidney compared with that in the salinetreated controls at the same ages. Cadmium at both doses caused extensive necrosis in the testes of adult rats, but not in newborn rats. In contrast, cadmium did not produce any observable changes in the morphology of other tissues at either age. The concentration of cadmium in the kidney, liver, adrenal, spleen, and heart of newborns treated with cadmium was lower than that of adults at comparable dosages. There was no difference in the concentration of cadmium in the testes, skeletal muscle and plasma of young adult and newborn rats. The concentration of cadmium in the lung, bone, brain, and blood of newborn rats was higher than that of young adults. There is an age difference in both the toxicity and tissue distribution of cadmium after subchronic administration to rats.