Determination by circuit analysis of cell membranes and junctional resistances in rabbit esophageal epithelium

AIM: The esophageal epithelium (EE) is regularly exposed to luminal environments of varying osmolality, pH, temperature and chemical composition, and as such needs a means of protection against injury. One factor that serves this purpose is the ability of the cell membranes and intercellular junctions to serve as barriers (resistors) to ion permeability. Indeed, though the EE is known to be an electrically tights tissue (avg. 2000 ohms:cm²), it would be of value to know the contribution to this resistance of its individual cell membranes and intercellular junctions. METHODS: To obtain these values, circuit analysis using the formula: R_T=(Ra+Rb) (Rs)/Ra+Rb+Rs was performed on Ussing chambered-rabbit EE. In some experiments serosal nystatin, a polyene monovalent ionophore, 0.1 mM, was used to permeabilize the basolateral membrane (Rb) to obtain apical membrane resistance (Ra) and NMDG-C1 solutions substituted for HEPES-buffered solutions to obtain shunt resistance (Rs). RESULTS: (Means±SEM, n=6). Ra was 5,248±115, Rb was 2635±457, and Rs was 4641±129 ohms:cm². From Ra+Rb, Rcell was calculated to be 7883±543. CONCLUSIONS: Since Rcell is almost double Rs, the shunt pathway represents the pathway of least resistance across EE. For this reason, when noxious environments, e.g. luminal HCl, reduce R_T in Ussing chambered EE, this is principally a reflection of increased shunt permeability and correlates well with increases in transepithelial mannitol fluxes.