Physiological concept for a blood based CFTR test

We tested the hypothesis that the cystic fibrosis transmembrane conductance regulator ( CFTR) could be involved in the volume regulation of human red blood cells (RBC). Experiments were based on two gadolinium (Gd3+) sensitive mechanisms, i.e. inhibition of ATP release (theta ATP(i)) and membrane destabilization. RBC of either cystic fibrosis (CF) patients or healthy donors (non-CF) were exposed to KCl buffer containing Gd3+. A significantly larger quantity of non-CF RBC (2.55 %) hemolyzed as compared to CF RBC (0.89 %). It was found that both of the Gd3+ mechanisms simultaneously are needed to achieve hemolysis, since either overriding theta ATP(i) by exogenous ATP addition prevented Gd3+ induced hemolysis, or mimicking theta ATP(i) by apyrase in absence of Gd3+ could not trigger hemolysis. Additionally, ion driven volume uptake was found to be a prerequisite for Gd3+ induced hemolysis as chloride and potassium channel blockers reduced the Gd3+ response. The results show that in non-CF RBC Gd3+ exerts its dual effect leading to hemolysis. On the contrary, in CF RBC, lacking CFTR dependent ATP release, the sole Gd3+ effect of membrane destabilization is not sufficient to induce hemolysis similar to non-CF. This concept could form the basis of a novel method suitable for testing CFTR function in a blood sample. Copyright (c) 2006 S. Karger AG, Basel.