Response of enzyme activities and metabolic intermediate concentrations to glucagon administration in hepatopancreas and muscle of carp
An experiment was carried out to investigate the effect of an intraperitoneal glucagon administration (60 μg/kg) on enzyme activities and metabolic intermediate concentrations in the hepatopancreas and muscle of common carp Cyprinus carpio. In the hepatopancreas, glycogen phosphorylase a activity together with cyclic adenosine-5′-monophosphate (AMP) concentration were significantly increased, and glycogen content was significantly decreased, at 1 h after the glucagon administration. Additionally, glucose-6-phosphatase and fructose-1,6-bisphosphatase activities as well as plasma glucose and free amino acid concentrations were increased after its administration. In the muscle, glucose and glycogen contents increased after the administration. Furthermore, the hormone administration also increased phosphofructokinase activity together with fructose-6-phosphate, AMP, and adenosine-5′-diphosphate concentrations and decreased adenosine-5′-triphosphate concentration. From 3 h after the administration, many parameter concentrations in both tissues showed a tendency to recover to the initial levels. These results suggest that glucagon administration enhanced glycogenolysis and gluconeogenesis in the hepatopancreas, and as a consequence, glucose was released into the bloodstream. The blood glucose seems to be metabolized through enhanced glycolysis and glycogenesis in the muscle.