The overall goal of this project is to determine the membrane mechanisms for intracellular pH regulation in human airway epithelial cells. Intracellular pHi regulates a variety of cellular processes including the function and activity of many ion transport mechanisms. Cystic fibrosis (CF) is a single gene defect which affects several ion transport pathways including the apical Na and Cl permeabilities, the Na, K-ATPase and possibly the basolateral K permeabilities. Intracellular pHi is a CF might be associated with a defect in the regulation of Intracellular pHi- regulatory mechanisms in human airway epithelium. The specific aims of the proposed research are: (1) To make reliable estimation of pHi in cultured normal and CF nasal epithelium. (2) to determine whether specific H and HCO3 transport pathway[s] ((Na/H exchange, Cl/HCO3 exchange, Na-HCO3 cotransport, and conductive H and HCO3 pathways) contribute to pHi regulation in nasal epithelium. The chemical and hormonal regulation of these mechanisms will also be determined. (3) To determine whether the ion transport pathways responsible for the control of Intracellular pHi are affected by CF. The method centers around the use of pH-sensitive fluorescent probes, microspectrofluorimetry, and digital image processing to measure pHi in single cultured human nasal cells.