IIb族元素(Zn²⁺、Cd²⁺、Hg²⁺)及びセレンのインスリン様作用について

抄録

Selenate was found to have several insulin-like effects in rat adipocytes: stimulation of glucose transport activity by translocation of two types of glucose transporters from intracellular sites to the plasma membrane, stimulation of cAMP phosphodiesterase activity, and stimulation of ribosomal S6 protein phosphorylation, Furthermore, in intact cells addition of 1mM selenate stimulated tyrosyl phosphorylation of 210-, 170-, 120-, 95-, 70-, and 60-kDa proteins but failed to stimulate insulin receptor kinase activity, suggesting that selenate stimulated other tyrosine kinase. In the presence of insulin, selenate enhances insulin receptor’ kinase activity and phosphorylations of insulin-stimulated tyrosyl phosphoproteins. These results may provide clues for the elucidation of the role of selenium in animals and the mechanism of insulin action.

Zn²⁺ (1mM) , Cd²⁺ (1mM) , and Hg²⁺ (0.1mM) belonging to the I b group in the periodic table stimulated glucose transport activity and cAMP phosphodiesterase in rat adipocytes. The stimulation of glucose transport was due to the translocation of glucose transporters from the intracellular site to the plasma membrane. However, in intact adipocytes none of these ions stimulated insulin receptor kinase activity or phosphorylation of the 95-kDa subunit of insulin receptor or 170- or 60-kDa proteins at the tyrosyl residues. These proteins were markedly phosphorylated by addition of 0.3nM insulin which stimulated glucose transport activity as effectively as these metal ions. These results indicate that Zn²⁺, Cd²⁺, and Hg²⁺ mimic insulin action by a post-receptor/ kinase mechanism.