Altered Erythrocyte Sodium Efflux following Renal Transplantation

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Abstract
Abnormalities of membrane Na transport are one of the manifestations of chronic renal failure. Following correction of renal failure by renal transplantation erythrocyte membrane NaK-ATPase activity increases to supranormal values. Direct measurements of erythrocyte Na efflux were performed in 21 renal transplant patients. The mean rate constant for total Na efflux was increased from 0.40 .+-. 0.01 in a group of control subjects to 0.45 .+-. 0.02 in transplant patients (P < 0.02). This increase in total Na efflux rate constant was attributed to an increase in the glycoside sensitive component of Na efflux which averaged 0.26 .+-. 0.01 in control subjects, compared to 0.32 .+-. 0.02 in transplant patients (P < 0.01). Intracellular Na was significantly lower in patients (5.8 .+-. 0.3 mmol/l of erythrocytes) than it was in controls (7.5 .+-. 0.2 mmol/l of erythrocytes). Overall pump flux was not increased in renal transplant patients, suggesting that a new steady state was established in their erythrocytes, with the red cell Na set at a new level. When normal erythrocytes were preincubated with plasma of renal transplant patients, all components of Na efflux remained normal. Plasma of renal transplant patients was ineffective in inducing a change in cell membrane NaK-ATPase activity in vitro. Following renal transplantation there were changes in erythrocyte Na transport, which were the obverse of those seen in uremia. They may represent overcompensation in a transport system previously exposed to prolonged uremic suppression.

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