Parathyroid hormone enhances glucagon secretion from the isolated perfused rat pancreas preparation

We examined whether PTH could increase glucagon secretion in an in vitro system, the isolated perfused rat pancreas. Since the response of the A cell has been shown to be modulated by antecedent exposure to elevated concentrations of glucose, bovine PTH (Beckman 1-34) was superimposed upon 15-min infusions of glucose followed by arginine or upon infusions of arginine alone. In the presence of PTH (44 ng/ml) and when the ambient calcium concentration was 9.0 mg/dl, arginine (168 mg/dl)-induced glucagon secretion was augmented. This occurred regardless of whether arginine was preceded by glucose (150 mg/dl). The glucagonotropic effect of PTH was absent in the presence of a low ambient calcium concentration (3.0 mg/dl). PTH failed to affect glucose-induced glucagon suppression.