Leucocyte sodium transport in acromegaly.

The leucocyte sodium pump was studied in patients with active and treated acromegaly. The ouabain-sensitive 22Na+ efflux rate constant was significantly raised in active acromegaly (median 2.71 [range 2.33-3.20] vs 2.32 [1.55-3.67] h-1, P less than 0.008) and was lowered into the normal range with successful treatment. Plasma GH and insulin levels and skin fold thickness on the dorsum of the hand were positively correlated with this efflux rate constant (rs = 0.06 P less than 0.02; rs = 0.57, P less than 0.02; rs = 0.57 P less than 0.04, respectively). GH, in vitro, stimulated ouabain-sensitive efflux in leucocytes at a concentration of 25 mU/l. We propose that this action of GH may explain the sodium retaining and calorigenic effects and possibly the stimulation of amino acid uptake by the hormone. The activity of the leucocyte sodium pump in acromegaly may be associated with other indices of disease activity.