Sepsis correlated with increased erythrocyte Na⁺ content and Na⁺-K⁺ pump activity

The aims of the present study were twofold: (1) simultaneous determinations of Na⁺ transport parameters of erythrocytes from 40 healthy donors and 28 septic patients as assessed by a score of severity of sepsis (SSS), and (2) examination of the correlation between the SSS and specific Na⁺ transport abnormalities. Erythrocytes were obtained and loaded with different ionic compositions and cellular Na⁺ contents before determination of the near-maximal Na⁺ pump rate (Vmax), the physiological extrusion rate of Na⁺(v) and the number of ouabain-binding sites (Bmax). In erythrocytes from septic patients, the cellular Na⁺ content was 28% higher (p < 0.001), with no differences in water content compared to erythrocytes from healthy donors. This elevated Na⁺ content was accompanied by significantly higher values for Vmax (43%), v (24%) and Bmax (48%) of the Na⁺ pump in septic erythrocytes. Moreover, significant positive correlations existed between Vmax and SSS (p = 0.028) and between cellular Na⁺ content and SSS (p = 0.005). These data suggest that during sepsis, membrane alterations occur and result in an increased cellular Na⁺ content. Active Na⁺ transport (Vmax and v) was significantly stimulated, possibly as a consequence of a secondary response to the elevated Na⁺ of cells. Both cellular Na⁺ and Vmax correlated well with the severity of sepsis, suggesting that these altered transport parameters may reflect the progress of sepsis.