Intracellular free calcium levels in mononuclear cells of patients with cystic fibrosis and normal controls.

The time course of resting free intracellular calcium concentrations in isolated mononuclear blood cells following a one hour incubation period with the fluorescent dye quin2 was evaluated. Under equal experimental conditions, a slow time-dependent increase of intracellular free calcium in patients with cystic fibrosis and normal healthy controls was noted. Using regression analysis, cystic fibrosis patients were seen to exhibit significantly higher free intracellular calcium concentrations than the controls over the time span covered. At an arbitrarily selected time (60 minutes) the free calcium level was 143.7 +/- 4.3 nM (SEM) in the patients, and 125.5 +/- 2.6 nM in controls. From these data it is concluded that neglecting the time-dependent (Ca2+)i changes following quin2 incubation leads to over- and/or underestimation of the unstimulated resting, basic free calcium levels and prevents the detection of differences between normals and cystic fibrosis patients.