Turnover, membrane insertion, and degradation of sodium channels in rabbit urinary bladder.

Noise analysis of rabbit bladder revealed two components: Lorentzian noise, arising from interaction of amiloride with the Na+ channel, and flicker noise (l/f, where f is frequency), as in other biological membranes. Hydrostatic pressure, which causes exchange between intracellular vesicular membrane and apical membrane, increases the number but not the single-channel current of the amiloride-sensitive channels. Flicker noise arises from degraded channels that have lost amiloride sensitivity and Na+ to K+ selectivity. The degraded channels were selectively removed by washing the mucosal surface. These results imply channel turnover by intracellular synthesis, transfer from vesicular to apical membrane, degradation, and elimination.