IDENTIFICATION OF TESTICULAR CELL PLASMA-MEMBRANE RECEPTORS FOR CALCITONIN

  • 1 January 1980
    • journal article
    • research article
    • Vol. 96  (5) , 933-938
Abstract
A role for CT [calcitonin] in the serum and tissue Zn homeostatic mechanism was suggested. The effects of CT on Zn transport appeared to be most pronounced in testis and thymus. If the effects are physiologically important, a cell membrane CT receptor, similar to those described for other peptide hormones, should be demonstrable. Rat testicular and hepatic cell membranes were isolated on a linear 15-50% sucrose density gradient. Specific hormone binding was assessed by Scatchard analysis of the binding of a constant amount of radiolabeled hormone in the presence of known variable amounts of unlabeled hormone. Nonspecific binding was assessed by measurement of radiolabeled hormone binding in the presence of 103 molar excess of unlabeled hormone. Hepatic cell membrane demonstrated no specific binding of either 125I-synthetic human CT or 125I-synthetic 1-34 bovine PTH [parathyroid hormone]. Testicular cell membranes demonstrated no specific binding for PTH. CT, however, was specifically bound with a mean Kd of 3.2 .+-. 0.8 .times. 10-8 (SEM) mol/l (M). Specificity studies demonstrated no inhibition of CT binding of 102 molar excess of follitropin, lutropin, 1-34 PTH or insulin. A specific plasma membrane receptor for CT may be present in rat testes. The presence of a membrane receptor in this tissue is consistent with previous observations that CT can alter the Zn content of rat testis in vivo.