Glucagon release: paradoxical stimulation by glucose during calcium deprivation.

During calsium deprivation, the rate of glucagon release by the isolated perfused rat pancreas is positively related to the glucose concentration of the perfusion medium. It is suggested that such a paradoxical behavior, which is reminiscent of the abnormality of glucagon secretion recently disclosed in diabetic subjects, results from a perturbation in the normal structural and functional bridging between pancreatic alpha and beta cells.