Decreased erythrocyte (Ca2+ + Mg2+)-ATPase activity in hemodialyzed uremic patients.

Erythrocyte (Ca2+ + Mg2+)-ATPase activity and calcium content were determined in 15 uremic-hemodialyzed patients and 15 normal controls. A decrease in the activity of the enzyme (mean +/- SD = 65 +/- 7 vs. 79 +/- 12 mumol Pi/g Hb/h, p less than 0.001) and a parallel increase in the calcium content (17.2 +/- 6.4 vs. 5.1 +/- 4.2 mumol/L RBC, p less than 0.05) were found in the patients' erythrocytes when compared with those of the controls. It is proposed that malfunction of the calcium pump in hemodialyzed uremic patients is pathophysiologically significant in the accumulation of intracellular calcium. The increased intracellular calcium found in other tissues in uremia may be the result of the systemic malfunction of (Ca2+ + Mg2+)-ATPase in this disorder.