Comparison of cadmium-saturation assay and radioimmunoassay for the determination of metallothionein concentration in tissues.

The more common Cd-saturation method for metallothionein (MT) analysis in tissues is compared with a recently developed radioimmunoassay (RIA). The Cd-saturation assay as described by others is fast, but less specific and accurate than the RIA. The former assay, previously used for MT analysis in urine and plasma, was modified to suit its use in measuring MT concentration in tissues. Liver and kidney from control rats were assayed and values of 7 and 67 micrograms/g were measured in the two tissues, respectively. The detection limit of the assay is 10 ng/g. A modified version of the Cd-saturation assay, which was limited with respect to the number of samples that can be analyzed at one time, gave results which were similar to the ones obtained by the RIA. The advantages and the problems associated with the two assays are discussed.