Cystic fibrosis decreases the apical membrane chloride permeability of monolayers cultured from cells of tracheal epithelium.

Abstract

The tracheal mucosa from a 12-year-old girl was digested from collagenase 4 hr after her death from cystic fibrosis. Fortymillion viable cells were obtained. The cells, plated at 106 per cm2 onto four Nuclepore filters coated with human placental collagen, formed confluent monolayers after 1 day. Their ultrastructure was similar to that of normal human cells. They were studied in conventional Ussing chambers or with intracellular microelectrodes on days 5-7 after plating. The monolayers displayed resistance of 380 .+-. 50 .OMEGA.-cm2 and short-circuit current (Isc) of 1.8 .+-. 0.4 .mu.A .cntdot. cm-2. This resistance is similar to that obtained for dog or normal human monolayers. The Isc is less than normal human (.apprxeq. 3 .mu.A .cntdot. cm-2) or dog (.apprxeq. 10 .mu.A .cntdot. cm-2) cells. The cystic fibrosis cells resembled normal monolayers in that serosal ouabain and mucosal amiloride inhibited Isc, while mucosal ouabain or serosal amiloride had no effect. They differed from normal human or dog cells in that Isc was not inhibited by bumetanide and the stimulation of Isc by isoproterenol or prostaglandin E2 was greatly reduced or abolished. Addition of isoproterenol depolarized apical membrane potential (.psi.a) and decreased fractional resistance (fR) in normal human and dog but had no effect on .psi.a or fR in cystic fibrosis cells. Reduction of mucosal chloride from 120 to 5 mM by replacement with gluconate increased fR of dog and normal human monolayers and depolarized .psi.a by 22 (dog) or 30 (human) mV. In cystic fibrosis monolayers, chloride replacement hyperpolarized .psi.a by 2 mV and had little effect on fR. These results suggest that the primary defect in cystic fibrosis is reduced apical membrane chloride conductance.