EFFECT OF THYROID STATUS ON OUABAIN BINDING TO THE HUMAN-LYMPHOCYTE

Abstract

Lymphocyte Na-K ATPase was evaluated as an index of thyroid status in man. Lymphocytes from 24 untreated hypothyroid patients and 11 hyperthyroid subjects were sampled in parallel with normal lymphocytes, and Na-K ATPase activity was assessed by measurements of ouabain binding to a plasma membrane fraction or to whole cells. In both systems, ouabain bound saturably and specifically, resulting in linear Scatchard plots. Normal lymphocyte plasma membranes bound 2.30 +/- 0.16 pmol ouabain/mg protein (mean +/- SEM; n = 11), with a Kd of 68 +/- 12 nM. Intact normal lymphocytes bound 3.24 +/- 0.30 pmol ouabain/10(7) cells (n = 14), representing 189,000 sites/cell. In hypothyroidism, ouabain bindin..