Biochemical changes in the liver of the Indian freshwater murrel, Channa punctatus (Bloch) during estradiol-induced vitellogenin synthesis

Estrogen administration in C. punctatus increases RNA: protein and RNA: DNA ratios and depletes glycogen in the liver. Increase in glucose-6-phosphatase activity accounts for glycogen depletion whereas high activity of pyruvate kinase suggests stimulation of the glycolytic pathway at the pyruvate step to generate ATP and to provide carbon skeleton for the vitellogenin molecule. Five-fold increase in the activity of NADP⁺-dependant malate dehydrogenase generates NADPH possibly for fatty acid synthesis. Additional energy requirement (NADPH) is met by stimulation of hexose monophosphate pathway as well as NADP⁺-dependant isocitrate dehydrogenase. Increase in the activity of NADPH-cytochrome c reductase in microsomal fraction suggests stimulation of electron transport chain. Increase in the activity of glutamate pyruvate transaminase can be directly related to the synthesis to specific amino acids needed for the formation of vitellogenin whereas reduction in glutamate oxaloacetate suggests extra hepatic source of amino acids. Reduction in the activity of glutamate dehydrogenase may be due to catabolism.