Cultured A6 epithelia and native Na+ transporting tissues exhibit large transient increases of short-circuit currents (Isc) during equilibration in Ussing chambers that require between 30-120 minutes to stabilize. In both control and aldosterone pre-treated A6 epithelia, peak currents averaged about twice those measured in inserts prior to mounting the tissues in the chambers, despite constancy of the growth medium bathing the tissues in the chambers and the inserts. To understand the nature of these transients, we used a pulse method of blocker-induced noise analysis to determine the changes of Na+ channel densities (NT), open probabilities (Po) and single-channel currents (iNa) during the equilibration periods as the currents returned towards those originally measured in the inserts. Underlying the changes of the Isc were large changes of iNa, Po and NT, mainly due in decreases in NT from 1117±527 to 103±32 channels/100 μm2 (control tissues, n=12) and from 2761±604 (n=8) to 220±19 (n=20) channels/100 μm2 for aldosterone-pretreated tissues within 40 minutes. Both Po and iNa increased during this time. iNa increased from 0.20±0.02 to 0.32±0.02 pA (control) and from 0.12±.0.01 to 0.30±0.01 pA (aldosterone). Po increased from 0.15±0.02 to 0.36±0.03 (control) and from 0.13±0.02 to 0.30±0.02 (aldosterone).
|Original language||English (US)|
|State||Published - Dec 1 1997|
ASJC Scopus subject areas
- Molecular Biology