Suppressive effect of excess dietary histidine on the expression of hepatic metallothionein-1 in rats.

The gene expression of liver metallothionein-1 in excess dietary histidine was investigated by feeding rats ad libitum on either a basal or histidine-excess (50 g of L-histidine per kg of diet) diet for 5 d. The copper content of the liver and zinc level in the serum of the rats fed on the histidine-excess diet were lower by 21% and 61%, respectively of the figures for the rats fed on the basal diet, but the zinc content of the liver and copper level in the serum were not affected. Excess dietary histidine caused an increase in the urinary output of both copper and zinc. The level of liver metallothionine-1 mRNA was markedly lower at 19% in the rats fed on the a histidine-excess diet compared to the level with the basal diet. It thus appears that such a response by the level of liver metallothionein-1 mRNA might have been be due to the lower content of liver copper.