LOCALIZATION OF AMILORIDE-SENSITIVE SODIUM-CHANNELS IN A6 CELLS BY ATOMIC-FORCE MICROSCOPY

Atomic force microscopy (AFM) was used for high-resolution imaging of the apical distribution of epithelial Na+ channels in A6 renal epithel ial cells. A6 cells grown on coverslips were labeled with antibodies g enerated against an amiloride-sensitive epithelial Na+ channel complex purified from bovine renal medulla that had been conjugated to 8-nm c olloidal gold particles before preparation for AFM. AFM revealed that there was a marked increase in the height of the microvilli in cells l abeled with the antiepithelial Na+ channel antibodies compared with un labeled cells or cells labeled with rabbit nonimmune immunoglobulin G conjugated to colloidal gold particles. We interpret this apparent inc rease in microvillar height to be due to antiepithelial Na+ channel an tibody binding to the apical microvilli. These data demonstrate that e pithelial Na+ channels are restricted to the apical microvilli in Na+- transporting renal epithelial cells. Furthermore, they demonstrate the applicability of using AFM for high-resolution imaging of the cell su rface distribution of epithelial ion channels.