Abstract
Summary
The effect of glucagon has been compared to rat thyrocalcitonin under experimental conditions which had produced information concerning the role of the latter hormone in bone metabolism. The dose-response curve shows that the minimum dose of glucagon needed to produce hypocalcemia produced a dramatic hypophosphatemia and a near-maximum glycogenolytic response. When intact, parathyroidectomized and thyroidectomized rats are treated with pharmacological doses of glucagon, plasma calcium and plasma phosphate changes are similar to those which occur after thyrocalcitonin treatment, thus eliminating the presence of parathyroid and thyroid glands as prerequisite for these effects. Since glucagon is effective in bilaterally nephrectomized animals, these changes can not be due solely to renal effects of the hormone. As with thyrocalcitonin, as the plasma phosphate rises, the hypocalcemic response to glucagon becomes more pronounced. In experiments using either 10-day or 18-hr radiophosphorus labels, glucagon produced a thyrocalcitonin-like action suggesting that, at the doses studied, glucagon may reduce bone resorption. It is concluded that large amounts of glucagon have a thyrocalcitonin-like effect which is probably neither physiological nor related to its primary action as a liver glycogenolytic agent.
We thank Mrs. Midge Raneri, Mrs. Beverly Lennon, Miss Barbara Ross, Mrs. Loralee Goyen, and Mrs. Nancy Haskins for their valuable technical assistance in this work.
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