Critical concentration of cadmium for renal toxicity in rats.

To evaluate a critical concentration concept of cadmium (Cd) toxicity on the kidney, relationships of renal Cd level with urinary excretion of various substances--i.e., metallothionein, alkaline phosphatase, lactate dehydrogenase, N-acetyl-beta-D-glucosaminidase, total protein, Cd, copper, and zinc--were studied in Cd-injected rats. At the renal Cd concentration of 100-200 micrograms/g tissue, a dramatic increase of all these substances in urine was observed, supporting the idea of the critical concentration proposed by Friberg and co-workers (1974). The significance of increase of urinary metallothionein below this level is also discussed.