Urinary metallothionein as an indicator of cadmium body burden and of cadmium-induced nephrotoxicity.

There is a need to identify specific biological indicator(s) of cadmium exposure so that the renal damage can be prevented. Towards this end, we have examined the usefulness of urinary metallothionein as an indicator of cadmium body burden. It is found that, in both animals and humans, urinary metallothionein level is related to the hepatic and renal cadmium burdens. Significant correlations are also found between the urinary metallothionein and urinary cadmium and beta 2-microglobulin. Furthermore, it is noted that cadmium-exposed individuals with renal dysfunction excrete significantly more metallothionein than those with normal renal function. Thus it appears that there is merit to include metallothionein among the clinical parameters monitored in cadmium-exposed individuals. More tests are needed to define a critical concentration of metallothionein in urine which is related to the onset of renal dysfunction.