Metabolic adaptation to prolonged starvation of carp.

Abstract

In order to clarify the biochemical aspects of metabloic adaptation to prolonged starvation in fish, carp Cyprinus carpio were starved for 30 days in a 800l fiber reinforced plastic aquarium, and changes in hepatopancreatic enzyme activities and body composition were determined. The protein content of the serum, hepatopancreas, muscle and whole body decreased gradually over the 30 day-period of starvation, whereas, the hepatopancreas glycogen content and serum triglyceride concentration decreased rapidly during first 7 days and remained low thereafter. However, the concentration of serum glucose remained almost constant throughout the starving period, and the concentrations of serum free amino acid and free fatty acid increased gradually. The activities of hepatopancreatic glucosephosphate isomerase, glucose-6-phosphate dehydrogenase, phosphogluco-nate dehydrogenase, NAD-and NADP-malate dehydrogenases, and NAD-isocitrate dehydrogenase were significantly decreased during starvation, whereas, activities of glucose-6-phosphatase, glutamic pyruvic transaminase and glutamic oxaloacetic transaminase were similar to or higher than those in prestarvation. These data indicate that, during starvation, glycoloysis, lipogenesis and energy production markedly decrease, while gluconeogenesis and amino acid degradation remain and continue to supply glucose in the hepatopancreas. Also, during prolonged starvation, the body protein and lipid are consumed as energy sources after an exhaustion of glycogen.