⁸⁶Rb(K) influx and [³H]ouabain binding by human platelets: Evidence for β-adrenergic stimulation of Na-K ATPase activity

Although active transport of potassium into human platelets has been demonstrated previously, there is hitherto no evidence that human platelets have an ouabain-inhibitable Na-K ATPase in their membrane. The present study demonstrates active rubidium (used as an index of potassium influx), ⁸⁶Rb(K), influx into platelets, inhibitable by ouabain, and also demonstrates the presence of specific [³H]ouabain binding by the human platelet. This ⁸⁶RB(K) influx was stimulated by adrenaline, isoprenaline, and salbutamol, but noradrenaline caused a mild inhibition. Active ⁸⁶Rb(K) influx by platelets was inhibited markedly by timolol, mildly by atenolol, but not by phentolamine. Therefore, active ⁸⁶Rb(K) influx in human platelets is enhanced by stimulation of β adrenoceptors of the β₂ subtype. The platelet may therefore replace the leukocyte in future studies of Na-K ATPase activity. This would be a considerable advantage in view of the ease and rapidity of preparation of platelets.