Analysis of interaction between insulin binding and insulin effect on primary culture of normal and db/db mouse...

Insulin binding and the characteristics of insulin receptors were studied in primary cultures of hepatocytes isolated from genetically diabetic mice (db/db mice). In addition glycogen synthesis in these hepatocytes was studied as one of the indicators of insulin action after binding to the receptors. The maximum insulin binding of db/db mice hepatocytes was 46% of control. There was no significant difference in insulin binding affinity between db/db and normal mice hepatocytes. In db/db mice, no insulin effect on glycogen synthesis was recognized. On the contrary, in the experiment on hepatocytes from normal mice exposed to insulin to induce down-regulation of insulin receptors (insulin-pretreated), the effect of insulin on glycogen synthesis was less but maintained. After re-culture of the insulin-pretreated hepatocytes with insulin-free medium, insulin binding and the insulin effect were restored. However, no apparent changes of insulin binding or the insulin effect on glycogen synthesis were recognized in hepatocytes from db/db mice under the same condition. These results suggested that the impaired process after insulin binding might play an important role, in addition to the decreased capacity of insulin binding, in the pathogenesis of DM in db/db mice.