[Changes in plasma glucagon concentration in patients with diabetes mellitus and its clinical significance].

To investigate the role of glucagon in the pathogenesis of diabetes, we observed change of plasma glucagon concentrations during glucose loading in normal subjects and patients with impaired glucose tolerance (IGT) and non-insulin dependent diabetes mellitus (NIDDM) using specific radioimmunoassay. The results showed that the fasting plasma glucagon levels in patients with IGT and NIDDM were similar to those of the normal subjects. The nadir of plasma glucagon level in the normal control occurred at 1-h after glucose loading and the changes of glucagon, glucose and insulin levels synchronized; but peaks of plasma glucose and insulin levels in the IGT and NIDDM patients were delayed at 2-h after glucose loading with the lowest glucagon level at 3-h. It was suggested that there were relative hyperglucagonemia and decrease of sensitivity of islet A cell to glucose in IGT and NIDDM patients. The present study also showed that hyperglucagonemia is related to the reduction of insulin secretion and might play an important role in the development of postprandial hyperglycemia in NIDDM.