Induction of cytoplasmic and mitochondrial enzymes by thyroid hormone in a freshwater catfish

Abstract

The activities of the cytoplasmic malate dehydrogenase, mitochondrial malate dehydrogenase and lactate dehydrogenase in the liver and the skeletal muscle of a freshwater catfish, Clarias batrachus, were studied in response to administration of triiodothyronine (T3). The activities of all the three enzymes in both tissues of the fish exposed to thiouracil for 28 days decreased 2 to 3 times as compared to normal individuals. A single injection of T3 to thiouracil exposed fish produced several fold increase in the activities of these enzymes. The induction of enzymes by T3 in the liver (7 to 9-fold) and the skeletal muscle (5 to 6-fold) was inhibited completely by actinomycin D and cycloheximide indicating T3-induced synthesis of the enzymes.