Pathway-specific response to cortisol in the metabolism of catfish.
Cortisol produced biochemical pathway-specific effects on metabolic enzymes and other macromolecules in the freshwater catfish, Clarias batrachus. Injection of cortisol increased 1.6-fold activity of citrate synthase (CS) in brain, liver and skeletal muscle of the fish over vehicle-injected control, while administration of metyrapone (a cortisol synthesis inhibitor) reduced CS activity by 52%. Cortisol treatment of metyrapone-treated fish induced CS activity by approximately 2.5-fold, which was blocked after administration of actinomycin D or cycloheximide. This shows de novo synthesis of CS to enhance aerobic capacity of fish. In contrast the activities of glucose-6-phosphate dehydrogenase (G6-PDH) and lactate dehydrogenase (LDH) increased in response to metyrapone and decreased after administration of cortisol in all the three tissues. The cortisol-mediated decrease in G6-PDH and LDH activities reflects reduction in biosynthetic and anaerobic capacity of fish. Administration of metyrapone significantly increased RNA/DNA ratio and protein but cortisol decreased these macromolecular contents in brain, liver and skeletal muscle. It shows cortisol-induced decrease in protein synthesis capacity of fish. The present study suggests that cortisol-induces catabolic and aerobic but inhibits anabolic and anaerobic processes in freshwater catfish. The cortisol-dependent metabolic responses may also be associated with the permissive effect of cortisol on other hormone(s) in fish.
Tripathi
G
G
Department of Zoology, JNVyas University, Jodhpur 342001, India. drgst@rediffmail.com
Verma
Priyanka
P
D000818:Animals; D001921:Brain / Q000187:drug effects / Q000201:enzymology*; D002397:Catfishes / Q000378:metabolism*; D002950:Citrate (si)-Synthase / Q000378:metabolism; D003513:Cycloheximide / Q000494:pharmacology; D003609:Dactinomycin / Q000494:pharmacology; D005954:Glucosephosphate Dehydrogenase / Q000378:metabolism; D006854:Hydrocortisone / Q000037:antagonists & inhibitors / Q000494:pharmacology*; D007770:L-Lactate Dehydrogenase / Q000378:metabolism; D008099:Liver / Q000187:drug effects / Q000201:enzymology*; D008797:Metyrapone / Q000494:pharmacology; D018482:Muscle, Skeletal / Q000187:drug effects / Q000201:enzymology*; D011500:Protein Synthesis Inhibitors / Q000494:pharmacology; D012313:RNA / Q000096:biosynthesis; D015398:Signal Transduction
D011500:Protein Synthesis Inhibitors; D003609:Dactinomycin; D012313:RNA; D003513:Cycloheximide; D007770:L-Lactate Dehydrogenase; D005954:Glucosephosphate Dehydrogenase; D002950:Citrate (si)-Synthase; D006854:Hydrocortisone; D008797:Metyrapone