Reversed anion selectivity in cultured cystic fibrosis sweat duct cells

Abstract

The human genetic disease cystic fibrosis (CF) is characterized by defective epithelial Cl- conductance (GCl). To distinguish the CF-affected GCl from other Cl- channels, we have studied the properties of GCl in normal and CF cells grown from explanted reabsorptive sweat ducts (RD). The cultured cells from normal subjects retained some of the typical duct cell properties. The Na+ conductance inhibitor amiloride hyperpolarized intracellular potentials (Vm) by 10.4 +/- 1.6 mV (n = 12). Substitution of gluconate for Cl- depolarized Vm by 15.5 +/- 1.1 mV (n = 33). The apparent GCl (G'Cl) of normal cells was sensitive to adenosine 3',5'-cyclic monophosphate (forskolin, 10(-6) M), as evidenced by a significant increase (63%, n = 9) in the Cl- gradient induced depolarization, and more selective for Cl- than I- (substitution of Cl- by I- depolarized Vm by 6.3 +/- 0.3 mV, n = 49). Although the cells from CF subjects were statistically indistinguishable from normal cells based on Vm (-18.5 +/- 1.2 mV, n = 49 vs. -20.1 +/- 1.8 mV, n = 28), CF cells expressed differences in G'Cl, responses to forskolin, and anion selectivity. CF cells had a significantly reduced G'Cl as indicated by blunted responses to imposed Cl- gradients (26% of normal, n = 28). In contrast to our observations in normal cells, the G'Cl of CF cells was insensitive to forskolin.(ABSTRACT TRUNCATED AT 250 WORDS)