Radioimmunoassay of metallothionein in rabbit, rat, mouse, Chinese hamster, and human cells.

We describe a competitive, solid-phase radioimmunoassay for metallothionein, which employs a rabbit antiserum directed against rat MT-2 to detect metallothionein (MT) from several different species (rabbit, mouse, rat, Chinese hamster, and human). The lower limit of detection of the assay for rat MT-2 was 0.7 ng; for rabbit MT-2 it was 2 ng. The method is capable of measuring both isoforms of MT (MT-1 and MT-2). When MT levels in rat and mouse tissues were estimated with this RIA and the silver-saturation method, both assays gave the same pattern of MT induction in control and cadmium-treated animals. Both methods measured high levels of MT in human liver samples. Chinese hamster ovary cells induced with cadmium also showed elevated MT expression. The detectability of MTs from a broad range of species is facilitated by the use of solid-phase MT, which has an avidity for the antiserum similar to that of the MT in the tested sample.