Potentiation by Antidiuretic Hormone (Vasopressin) of the Ability of Parathyroid Hormone to Stimulate the Proliferation of Rat Thymic Lymphocytes[*]

Abstract

Pure bovine parathyroid hormone (PTH) and synthetic lysine vasopressin, or antidiuretic hormone (ADH), stimulate the proliferation of rat thymic lymphocytes (thymocytes) maintained in vitro by a cyclic AMP-mediated process. PTH concentrations in the medium between 0.06 and 0.5 U/ml did not affect the flow of thymocytes into mitosis, but concentrations between 0.75 and 2.0 U/ml strongly (and maximally) stimulated this flow. When the culture medium contained a non-mitogenic concentration (5.0 mU/ml) of ADH, the mitogenic effectiveness of PTH was profoundly changed. In the presence of ADH, the lowest maximally stimulatory PTH concentration was reduced from 0.75 to 0.12 U/ml, but the higher PTH levels (0.75 to 2.0 U/ml) were no longer able to stimulate cell proliferation. Addition to the medium of a non-mitogenic concentration (10^-9 M) of cyclic AMP (the possible common mediator of PTH and ADH actions) also increased the mitogenic effectiveness of PTH, A possible mechanism by which ADH could alter PTH action and the general significance of such hormonal interactions for the control of cell proliferation in the animal are briefly discussed.

Stimulation of Thymic Lymphocyte (Thymocyte) Proliferation by PTH, ADH (Vasopressin) - Sensitization to PTH Mitogenic Action by ADH (Vasopressin) - Sensitization to PTH Mitogenic Action by Cyclic AMP

1 Issued as NRCC No. 11512.