Differential effects of thyroxine on metabolic enzymes and other macromolecules in a freshwater teleost

Abstract

The effects of thyroxine (T(4)) on citrate synthase (CS), glucose 6-phosphate dehydrogenase (G6-PDH), lactate dehydrogenase (LDH), DNA, RNA, and protein of various tissues were studied to elucidate the hormonal control of metabolism in a freshwater catfish, Clarias batrachus. T(4) did not produce any significant effect on DNA content of the fish. The CS, RNA, and protein contents of brain, liver, and skeletal muscle of the fish exposed to thiourea for 28 days decreased approximately 50-58% as compared to their levels in control individuals. Injection of T(4) to thiourea-exposed fish produced about three-fold increases in CS, RNA, and protein. These macromolecular inductions by T(4) were blocked by actinomycin D or cycloheximide. This suggests T(4)-induced de novo synthesis of macromolecules and stimulation of aerobic capacity. However, the activities of G6-PDH and LDH of brain, liver, and skeletal muscle of the fish exposed to thiourea increased two times that of the activities in control individuals. Administration of T(4) to thiourea-exposed fish reduced LDH and G6-PDH activities by about 64-74%, which reflects T(4)-dependent inhibition in anaerobic power and selective anabolic activities of the HMP pathway. These differential effects of T(4) on some metabolic enzymes and other important macromolecules may be to meet the other T(4)-induced responses in the freshwater catfish.

The Role of the Thyroid Axis in Fish

“…T 4 treatment promotes lipolysis, stimulates lipid mobilization, and decreases lipid stores (e.g., as seen by decreased total lipids and increased lipolytic enzyme activity) in coho salmon (344), and increases lipid efficiency, plasma cholesterol and triglyceride levels in Sterlet sturgeon (345). Body protein content decreases in European eel (glass stage) treated with THs (346), and walking catfish exposed to thiourea (347). THs also affect glucose and related carbohydrate metabolism pathways.…”

Effectivity of thyroxine and recombinant growth hormone on the growth of Siam-catfish larvae

“…Faktor-faktor yang memengaruhi aktivitas hormon tiroksin adalah dosis, cara pemberian hormon, kualitas makanan, waktu pemberian makanan, dan ukuran ikan (Tripathi & Verma, 2003). Menurut Khalil et al (2011) hormon tiroksin dapat merangsang laju oksidasi bahan makanan, meningkatkan laju konsumsi oksigen, meningkatkan pertumbuhan, dan mempercepat proses metamorfosis.…”

Interacting effects of pyrethroid and hormone on catalase and protein for toxicity amelioration in the freshwater fish, Clarias batrachus

“…Cortisol administration to fish increase 14 C-alanine incorporation into glucose and CO 2 in hepatocytes (Vijayan et al 1993(Vijayan et al , 1994Martínez-Porchas et al 2009). Similarly, thyroid hormones exert numerous metabolic effects on nearly all tissues of the body in vertebrates (Tripathi and Verma 2003b;Oommen et al 2006). They increase the metabolic activities in different tissues of a number of fish species (Higgs et al 1982;Tripathi et al 2009).…”