[Mechanism of enzymatic regulation of tyrosine turnover in hyperthermia]

Activities of tyrosine aminotransferase and phenylalanine hydroxylase were studied in rat liver tissue in hyperthermia. Effects of heliothermic and laboratory chamber heating treatments were studied using intact animals and the rats preadministered with the enzyme substrates or hydrocortisone and with a mixture containing the substrates and hydrocortisone. The hyperthermia led to activation of tyrosine aminotransferase and to inhibition of phenylalanine hydroxylase in liver tissue. More distinct alterations in the enzymatic activity were observed after heliothermic treatment as compared with the chamber heating. Tyrosine aminotransferase and phenylalanine hydroxylase of liver tissue, which are involved in regulation of tyrosine content in the body, appear to maintain the coll homeostasis under conditions of external high temperature.