Inhibition by Thyrocalcitonin (Calcitonin) of the Cyclic AMP-Mediated Stimulation of Thymocyte Proliferation by Epinephrine

Abstract

Epinephrine stimulates the proliferation of rat thymic lymphocytes maintained in vitro by a cyclic AMP-mediated process. The mitogenic action of epinephrine is completely inhibited by low concentrations (6.0 to 8.0 mU per ml) of a highly purified sample of porcine thyrocalcitonin (calcitonin). In view of the fact that the same low levels of thyrocalcitonin are known to inhibit the cyclic AMP-mediated mitogenic action of vasopressin and the similar physiologically important mitogenic action of parathyroid hormone, it is proposed that thyrocalcitonin (calcitonin) may be a general regulator of cyclic AMP-controlled cell proliferation in vivo. 1 Issued as NRCC No. 12099