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.
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