Résumé
Changes of liver enzyme histochemistry and characteristics of glucagon receptor on liver cell plasma membrane were observed in streptozotocin-induced diabetic rats. The results showed that glycogenolytic and glyconeogenetic enzyme activities of liver were increased in diabetic rats and were higher than those of normal rats. There were no marked differences concerning both low and high affinities of glucagon receptors between normal and diabetic rats, but the concentration of low affinity glucagon receptor was significantly higher for diabetic rats than for normal rats. Compared with untreated diabetic rats, the concentration of high affinity glucagon receptor was normalized and that of low affinity receptor decreased by 30. 6% in insulin-treated diabetic rats. The present study implies that: 1)DURING insulin deficiency the increase in liver glyconeogenesis may be one of the important factors to induce increment of liver glucose output; 2) the increase in glucagon receptor binding to liver in streptozotocin-induced diabetic rats may provide a cellular basis for the increased glycemic and ketonemic response to glucagon in insulin-deprived diabetics; 3) since in diabetic rats insulin treatment results in a reversal of increased glucagon binding, it is possible that insulin regulates the glucagon receptor either directly or through its effect on the plasma glucagon concentration.