Increased sodium-proton antiporter activity in patients with obstructive sleep apnoea

Cytosolic pH (pH(i)) and the activity of the sodium-proton antiporter (Na+/ H+ antiporter) were measured in lymphocytes from 22 patients with obstructi ve sleep apnoea and from 24 age-matched healthy subjects (Controls). The ce llular Na+/H+ antiporter was measured spectrophotometrically using a pH-sen sitive fluorescent dye after intracellular acidification using sodium propi onate. Resting pH(i) was similar in lymphocytes from patients with obstruct ive sleep apnoea and from controls (7.36 +/- 0.20, n=22; vs. 7.35 +/- 0.19, n=24; mean +/- SD). The Na+/H+ antiporter activity was significantly highe r in patients with obstructive sleep apnoea than in controls (11.87 +/- 3.2 6 x 10(-3) pH(i)/s vs. 4.38 +/- 1.40 x 10(-3) pH(i)/s; P < 0.0001). The app arent affinity of the Na+/H+ antiporter was not significantly different bet ween the groups (6.90 +/- 0.23 vs. 6.87 +/- 0.20). In patients with obstruc tive sleep apnoea the activity of the Na+/H+ antiporter remained stable dur ing the night. The activity of the Na+/H+ antiporter was 13.49 +/- 4.80 x 1 0(-3) pH(i)/s at 20.00 and 13.26 +/- 6.13 x 10(-3) pH(i)/s at 02.00. From t he present results it is concluded that an increased cellular Na+/H+ antipo rter activity may be a genetic marker for patients who are predisposed to o bstructive sleep apnoea.