Nutritional influence on the onset of renal damage due to long-term administration of cadmium in young and adult rats.

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Abstract
This study was conducted to examine the effects of certain nutritional variables on the onset of renal damage due to oral administration of Cd, and to investigate its reversibility by dietary switch-over in female rats during an observation period of 7 mo. Four dietary regimens were adopted. Two basal diets, including a multinutritionally deficient diet (10% protein, 0.05% Ca, 0.14% P and no fiber) (designated L) and a normal balanced stock diet (designated N); each diet was fed with and without the addition of Cd 200 ppm, and then the 4 diets were designated L(-), N(-), L(+) and N(+). (+) indicates the addition of Cd, while (-) is without addition of Cd. In comparison with the N(+) group, rats fed the L(+) diet for 7 mo. revealed various distinct characteristics: marked growth retardation due mainly to decreases in food intake and food efficiency (Cd-induced protein-calorie malnutrition); marked depilation, general or localized, due to abnormal behavior of biting and eating each other''s hair; progressive increase in Cd output in urine, particularly 5 mo. after starting the dietary treatment and an increased output of urinary protein; and significant elevation of accumulated Cd in the kidney (and also in the liver). These observations were further supported by switch-over experiments, showing that the above-mentioned changes were reversed to normal when L(+) diet was replaced by either the L(-) or even the N(+) diet, whereas the abnormal changes became evident when the diet was switched to the L(+) diet 3 mo. after the experiment. Renal accumulation of Cd was remarkably increased in the L(+) group, despite much less Cd intake than in the N(+) group. Nutritional factor(s) probably play an important role in the early development of Cd poisoning, in particular in the development of renal damage, presumably due to enhanced input of Cd in the body.