Effect of short term triiodothyronine administration on human leukocyte rb(k) influx and na efflux

The effect of short term T₃ administration on leukocyte ouabain-sensitive ⁸⁶Rb(K) influx and Na efflux in normal subjects was investigated. At a dose of 60 μg daily for 7 days, T₃ induced a significant increase in leukocyte ⁸⁶Rb(K) influx and a significant fall in plasma K concentrations. Plasma and intracellular Na concentrations did not change. [³H]Ouabain binding, a measure of Na-K ATPase units, did not change. A week after T₃ administration, ⁸⁶Rb(K) influx, Na efflux, and plasma K concentrations were normal. In a series of five hyperthyroid patients, both ouabain-sensitive ⁸⁶Rb influx and [³H] ouabain binding were significantly greater than in normal subjects. We conclude that T₃ stimulates ⁸⁶Rb(K) influx and Na efflux by leukocytes in vivo independently of [3H]ouabain binding and that this increase is rapidly reversible. However, in hyperthyroid patients both ⁸⁶Rbinflux and [³H] ouabain binding are increased, probably due to prolonged exposure to thyroid hormone excess.