IMPAIRMENT OF SODIUM-PUMP AND NA+ H+ ANTIPORT IN ERYTHROCYTES ISOLATED FROM CANCER-PATIENTS/

We sought to determine whether the impairment of sodium pump activity and Na+/H+ exchange reported in tumorigenic cells was specific to thes e cells or more general, Sodium pump activity and Na+/H+ exchange were measured in erythrocytes from 49 cancer patients and 51 healthy subje cts, Cancer patients with a newly detected cancer or in relapse and wi thout associated pathologies known to modify these sodium transporters were included in this study. Two sodium pump statuses reflecting its physiological modulation were evidenced for healthy subjects (10.3 +/- 0.2 and 19.4 +/- 0.8 mW/liter of cells). In cancer patients, only one basal status lower than those of controls was observed (8.3 +/- 0.5 m W/liter of cells; P < 0.001). Cooperativity of the Na+/H+ antiporter i s the same in cancer patients and controls (2.58 +/- 0.27 versus 2.60 +/- 0.15). The intracellular pH (pH(i)) dependence curve of the antipo rter was shifted toward more acidic values, and optimal pH(i) was lowe r in cancer patients than in controls (5.80 +/- 0.03 versus 6.08 +/- 0 .02; P < 0.0001). The mean maximal rate and the K-m of H+ for the Na+/ H+ antiporter were higher: 8.4 +/- 1.2 versus 4.6 +/- 0.4 mmol H+/lite r of cells/h (P < 0.01) and 514 +/- 12 versus 322 +/- 16 nM (P < 0.05) , respectively. Alterations of these Na+ transporters, therefore, were not restricted to cancerous cells. Among the alterations, the acidic shift in the pH, dependence of Na+/H+ exchange appears associated with cancer because this behavior has never been reported in other patholo gies.