SHORT-TERM EFFECTS OF 3,5,3'-TRIIODOTHYRONINE ON THE ACTIVITY OF SELECTED ENZYMES OF INTERMEDIARY METABOLISM IN THE LIVER OF THE ATLANTIC HAGFISH, MYXINE GLUTINOSA

The short-term effects of 3,5,3'-triiodothyronine (T-3) on the interme diary metabolism of the liver of the Atlantic hagfish (Myxine glutinos a) were assessed by intraperitoneal injection of T-3. Three hours post injection, plasma T-3 concentrations and the activities of key enzymes involved in glycolysis, lipid catabolism, and amino acid and oxidativ e metabolism were measured. Plasma T-3 levels were significantly highe r (P < 0.05) in T-3-treated fish when compared to control and pretreat ment fish. T-3-treated fish had significantly higher (P < 0.05) activi ty of a pentose phosphate shunt enzyme, glucose-6-phosphate dehydrogen ase, than control fish. The activity of an enzyme of lipid catabolism, carnitine palmitoyl transferase, increased significantly (P < 0.05) a bove that of the controls in fish treated with a low T-3 dose. Other e nzymes of amino acid metabolism and oxidative metabolism were not affe cted by T-3 treatment. In the short-term, T-3 may modulate intermediar y metabolism in the liver by increasing the catabolism of lipids to su pply the energy requirements of biosynthetic processes. (C) 1997 Wiley -Liss, Inc.