Ouabain-sensitive and oligomycin-sensitive adenosine-triphosphatase activities of normal human lymphocytes.

Abstract

Summary. Homogenates of highly purified normal human lymphocytes contained two different adenosinetriphosphatase (ATPase) activities. One of these activities was present in a supernatant fraction of the lymphocyte homogenates, possibly related to mitochondria. This activity was independent of the presence of monovalent cations, was insensitive to ouabain, but was inhibited by oligomycin and stimulated by 2,4 dinitrophenol. Exchange of Mg++ with Ca++, or addition of sodium fluoride completely inhibited this ATPase activity. A Km‐value for the substrate ATP was determined to be 0.83 mm. The specific activity of the oligomycin‐sensitive, supernatant ATPase was 0.31 ± 0.13 (SD) μmoles Pi per mg protein per 30 min.The other ATPase activity was activated by Na+ and K+ and was inhibited by ouabain. This ATPase activity was only found in the pellet fraction after centrifugation, possibly associated with the cell membranes. The specific activity of this ATPase was 0.25 ± 0.09 (SD) μmoles Pi per mg protein per 30 min. The effect of ouabain in various cation combinations of the assay is reported. Optimal ouabain‐sensitive ATPase activity was found at 100 mm Na+, 15 mm K+ and 6 mm Mg++.Only the oligomycin‐sensitive ATPase activity increased after short time stimulation of the lymphocytes by phytohaemagglutinin (PHA), and this could be inhibited by puromycin.The increased ATPase activity of normal lymphocytes caused by the non‐specific mitogen PHA suggest the possibility that the increased ATPase activity of lymphocytes from patients with malignant tumours could be due to a stimulation of the lymphocytes by tumour specific antigens in vivo.