Metallothionein induction in rat liver by dietary restriction or exercise and reduction of exercise-induced hepatic lipid peroxidation.

Metallothioneins (MTs) occur throughout the animal kingdom and they are induced in vivo by metals, hormones, cytotoxic agents, and some kind of stress. It is well known that various stresses such as starvation and immobilization can induce MT synthesis in animal tissues, but the influence of dietary restriction is unknown. The MT levels in the liver increased by food-deprivation and then decreased by refeeding, and a long period of starvation down-alters hepatic MT levels. When the stress is intensified, the induced quantity of hepatic MT is reduced. It became clear that hepatic MT concentrations are controlled within a two fold limit when stressed by dietary restriction. MT was also induced in rat liver at recovery stage following an exhaustive running exercise, and thionein was synthesized first and then zinc bound to the protein. The half-life of hepatic MT induced by exercise (which is a nonmetallic inducer) was estimated at 5.2 h. Preinduced MT markedly suppressed exercise-induced lipid peroxidation in rat liver.