Chromium, Cadmium and Lead in Rats:

Abstract

Groups of 50 or more Long-Evans rats in a low metal environment and fed a diet devoid of cadmium and low in many trace metals were given 5 ppm chromium (III), cadmium or lead in drinking water from weaning until death. Life span was shortened in those fed lead and cadmium; tissue concentrations were within human ranges. Longevity of the last 10% was increased in those fed chromium; tissue concentrations were within ranges of young human beings, and females resisted an epidemic of pneumonia. Rats fed lead had fewer tumors than controls or other groups. Arteriolar sclerosis in kidneys and ventricular hypertrophy occurred largely in cadmium-fed animals; cirrhosis of the liver in all groups. Organs of controls were cadmium-free; the metal occurred in animals from another laboratory. Cadmium did not accumulate in kidneys at older ages. Older rats fed lead showed less in organs than younger ones. Chromium did not accumulate in tissues. Extension of life span by restriction of food was reproduced by restriction of lead and cadmium and feeding of chromium. Results indicate that lead and cadmium at human tissue concentrations are toxic to rats in terms of life span and longevity, whereas chromium (III) is not.