Erythrocyte Li-Na countertransport in uremic patients: effect of urea.

Abnormalities of erythrocyte cation transport systems including Li-Na countertransport have been described in uremic patients. Dialysis appears to eliminate the difference in some of the patients. We investigated the rate of Li-Na countertransport from erythrocytes of normal healthy subjects and uremic patients undergoing hemodialysis treatment. We found that erythrocytes from uremic patients exhibited a significantly elevated rate of Li-Na countertransport. Furthermore, urea (30 mM) did not affect the rate of Li-Na countertransport or the electrolyte contents for Li loaded erythrocytes. Our findings showed that while both plasma and urea concentration and erythrocyte Li-Na countertransport were elevated in uremic patients, urea was not the major cause of the enhanced activity of the transporter.