Acute changes in plasma immunoreactive insulin (IRI) and immunoreactive glucagon (IRG) levels in the pancreatic vein of dogs were studied following rapid pulse injections of CaCl2, KCl and glucose into the pancreatic artery. Blood from the pancreatic vein was taken continuously by changing the collection tubes every five seconds. IRI secretion was stimulated by all three agents within thirty seconds, while IRG secretion was stimulated by the injection of KCl but not by CaCl2 or glucose. Detailed comparisons of IRI responses revealed that IRI release occurred most rapidly after the injection of KCl and most slowly after the injection of glucose. Stimulation of IRI and IRG release occurred simultaneously after KCl injection. The data suggest that potassium stimulates α and β cells directly, without increasing calcium influx. The slower insulin-releasing effect of glucose, as compared with the cations, supports the theory that glucose acts by increasing calcium uptake.

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