Changes in activities of hepatic enzymes related to carbohydrate metabolism of fishes in glucose and insulin-glucose tolerance tests.

Abstract

In order to investigate the changes in activities of hepatic glycolytic and gluconeogenic enzymes after feeding and the responses of these enzymes to insulin injectin, carp Cyprinus carpio, red sea bream Chrysophrys major, and yellowtail Seriola quinqueradiata were subjected to glucose tolerance and insulin-glucose tolerance tests after a 30-day feeding trial with diets containing 0% and 10% dextrin. Activities of glycolytic enzymes (hexokinase and PFK) and gluconeogenic enzymes (G6Pase and FDPase) increased after the administratin of glucose in all species. The enzyme activities were intensified or restrained by the insulin injectin. No significant differences between the fish species were recognized for hexokinase and G6Pase activities before or after the administration of glucose, nor for the response of the enzymes to the insulin injectin. PFK activity before and after the administration of glucose was lowest and its response to the insulin injection was highst in yellowtail, in which the optimum level of dietary dexrin was the lowest of the species tested. PFK of carp showed the highest activity and FDP ase of carp showed the lowest activity before and after the administratin of glucose.