Evaluation of peripheral metabolic status by determination of Na-K ATPase pump activity in circulating erythrocytes in patients with thyroid diseases and nonthyroidal illnesses.

The number of Na-K ATPase units in erythrocytes (RBC) was determined by the maximal ouabain binding assay in 25 normal subjects and patients with hyperthyroidism (n = 29), hypothyroidism (8), chronic renal failure (CRF, 19) and with neoplastic disorders (NP, 12). The activity of the pump units was also assessed by measuring ouabain-sensitive 86Rb uptake in some of these subjects. In addition, it was determined in mononuclear cells in normal controls and patients with hyper- and hypothyroidism and CRF. Significant diminution of the number of the RBC pump units was found in hyperthyroidism, while it was increased in hypothyroidism. The binding (O) of old RBC was significantly lower than that (Y) of young RBC and a striking correlation was observed between the % reduction rate ((Y-O)/Y) of the binding and the serum T4 level in hyperthyroidism (r = 0.85, P < 0.02). No difference was observed in pump units of mononuclear cells in normal and hyper- and hypothyroidism. It is suggested that the thyroid hormone- mediated disappearance of the pump units in RBC may play a role in reducing the number of pump units in RBC in hyperthyroidism. The ratio of RBC 86Rb uptake to the number of the pump units in the same cell (U/B) bore a significant relation to serum T3 (r = 0.48, P < 0.05) and T4 (r = 0.49, P < 0.05) indicating that the U/B is a useful index for the peripheral metabolic status. In CRF patients with low T3 levels, bindings were increased but those in NP with low T3 was almost normal.(ABSTRACT TRUNCATED AT 250 WORDS)