Fluid absorption related to ion transport in human airway epithelial spheroids

Airway epithelium explants from cystic fibrosis (CF) patients and non-CF su bjects formed monolayered spheres, with the apical ciliated cell membrane f acing the bath and the basolateral cell membrane pointing toward a fluid-fi lled lumen. With the use of two microelectrodes, transepithelial potential difference and changes in potential difference in response to passage of cu rrent pulses were recorded, and epithelial resistance and the equivalent sh ort-circuit current were calculated. Non-CF central potential difference an d short-circuit current, values were significantly lower than the CF values , and amiloride inhibited both values. Fluid transport rates were calculate d from repeated measurements of spheroid diameters. The results showed that , 1) non-CF and CF spheroids absorbed fluid at identical rates (4.4 mu l.cm (-2).h(-1)), 2) amiloride inhibited fluid absorption to a lower residual le vel in non-CF than in CF spheroids, 3) Cl--channel inhibitors increased flu id absorption in amiloride-treated non-CF spheroids to a level equal to tha t of amiloride-treated CF spheroids, 4) hydrochlorothiazide reduced the ami loride-insensitive fluid absorption in both non-CF and CF spheroids, and 5) osmotic water permeabilities were equal in non-CF and CF spheroids (simila r to 27 x 10(-7) cm.s(-1).atm(-1)).