Increased Na+/Mg2+ antiport in erythrocytes of patients with cystic fibrosis.

Na+/Mg2+ antiport and Na(+)-independent Mg2+ efflux were investigated in erythrocytes of 41 patients with cystic fibrosis and 26 controls. Na(+)-independent Mg2+ efflux was unchanged in cystic fibrosis, but a significantly increased activity of Na+/Mg2+ antiport was detected (control: 0.16 +/- 0.02, cystic fibrosis: 0.39 +/- 0.06, Mg2+ efflux, mmol/30 min x 1 cells, mean +/- SEM, p < 0.01). An increased activity of Na+/Mg2+ antiport was only found in patients with severe clinical symptoms. There was no correlation of the increased Na+/Mg2+ antiport to the dF508 genotype. In a patient with increased Na+/Mg2+ antiport, the capacity of this transport system was unchanged 14 weeks after double lung transplantation but reached control values after 53 weeks. The sweat of cystic fibrosis patients with severe clinical symptoms showed a significantly increased Mg2+ concentration (control (n = 12): 0.053 +/- 0.08, cystic fibrosis (n = 9): 0.123 +/- 0.016 mmol/l, mean +/- SEM, p < 0.001).