Metallothionein content and zinc status in various tissues of rats treated with iodoacetic acid and zinc.

Metallothionein (MT) content was determined in 11 tissues of saline-treated rats, and 18 h after single IP injections of iodoacetic acid (IA, 15 and 30 mg/kg) or zinc sulfate (20 mg zinc/kg). Zinc increased MT content in eight tissues, being most effective in pancreas, liver, and small intestine. After IA, MT increased in liver, muscle, pancreas, and thymus, the highest amount being in liver. Increased levels of total tissue zinc were observed in those tissues which clearly responded to the treatments with elevated MT levels, such as liver, kidney, small intestine, and pancreas. MT induction by zinc in these tissues was associated with an accumulation of zinc not bound to MT. In the IA-treated rats non-MT zinc accumulated in liver and pancreas. It is concluded that induction of MT by zinc and in particular by organic chemicals such as IA without exogenously supplied metals interferes with zinc homeostasis and the physiological role of MT in liver and extrahepatic tissues of the rat.