| Autor: |
Wills, N. K., Millinoff, L. P. |
| Zdroj: |
Pflügers Archiv European Journal of Physiology; July 1990, Vol. 416 Issue: 5 p481-492, 12p |
| Abstrakt: |
Electrical techniques were used to determine the Na:K selectivity of the amiloride-sensitive pathway and to characterize cellular and paracellular properties of A6 epithelium. Under control conditions, the mean transepithelial voltage (VT) was -57±5 mV, the short-circuit current (Isc) averaged 23±2 µA/cm2 and the transepithelial resistance (RT) was 2.8±0.3 kOcm2 (n=13). VT and Isc were larger than reported in previous studies and were increased by aldosterone. The conductance of the amiloride-sensitive pathway (Gamil) was assessed before and after replacement of Na+ in the mucosal bath by K+, using two independent measurements: (1) the slope conductance (GT), determined from current-voltage (I-V) relationships for control and amiloride-treated tissues and (2) the maximum amiloride-sensitive conductance (Gmax) calculated from the amiloride dose-response relationship. The ratio of Gamil in mucosal Na+ solutions to Gamil for mucosal K+ solutions was 22±6 for GT measurements and 15±2 for Gmax data. Serosal ion replacements in tissues treated with mucosal nystatin indicated a potassium conductance in the basolateral membrane. Equivalent circuit analyses of nystatin and amiloride data were used to resolve the cellular (Ec) and paracellular (Rj) resistances (~5 kOcm2 and 8–9 kOcm2, respectively). Analysis I-V relationships for tissues depolarized with serosal K+ solutions revealed that the amiloride-sensitive pathway could be described as a Na+ conductance with a permeability coefficient (PNa)=1.5±0.2× 10-6 cm/s and the intracellular Na+ concentration (Nai)=5±1 mM (n=5), similar to values from other tight epithelia. We conclude that A6 epithelia are capable of expressing large amiloride-sensitive currents which are highly Na+ selective. |
| Databáze: |
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