SODIUM PUMP TRANSPORT ACTIVITY AND Na⁺, Ê⁺-ATPase EXPRESSION IN ACTIVATED HUMAN LYMPHOCYTES

I. I. Marakhova, I. I. Karitskaya, T. A. Vinogradova, N. D. Aksenov, A. V. Moshkov, A. L. Khaidukova

Institute of Cytology RAS, St. Petersburg, Russia;
e-mail: iim@mail.cytspb.rssi.ru

Ouabain-inhibitable rubidium influxes, intracellular sodium content (Na_i, and α1-subunit abundance have been studied in human blood lymphocytes, stimulated by phytohemagglutinin (PHA) or by the phorbol 12,13-dibutyrate (PDBu), and calcium ionophore - ionomycin. It is shown that at early stages of PHA-induced activation, the Na/K pump expression (as determined by Wesrn blots of al protein in membrane fractions of total cell lysates) does not change, and the increase in Rb influx is due to the increase in Na, and results from the enhanced transport activity of Na/K pumps present in plasma membrane. During the late stages of G₀→ G₁→ S transit (16-48 h), the increase in Rb influx occurs without changes in Na_i, and monensin increases both Na_i, and the Rb influx via the Na/K pump. To the end of the first day of mitogen activation, the α1 protein content was found to increase by 5-7 times. A correlation was revealed between changes in ouabain-inhibitable Rb influxes, α1 protein abundance, and the proliferation rate. It is concluded that blasttransformathion of normal human lymphocytes is accompanied by the increase in membrane-associated pool of α1-subunit of Na⁺, Ê⁺-ATPase, and the enhanced activity of sodium pump during the G₀→ G₁→ S progression is provided by increased number of Na⁺, Ê⁺-ATPase pumps in plasma membrane.

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