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Am J Physiol Cell Physiol 264: C1128-C1136, 1993;
0363-6143/93 $5.00
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AJP - Cell Physiology, Vol 264, Issue 5 C1128-C1136, Copyright © 1993 by American Physiological Society

ARTICLES

Artifactual expression of maxi-K+ channels in basolateral membrane of gallbladder epithelial cells

J. Copello, F. Wehner and L. Reuss
Department of Physiology and Biophysics, University of Texas Medical Branch, Galveston 77555-0641.

To patch clamp the basolateral cell membrane, sheets of Necturus gallbladder epithelium were stripped of the subepithelial tissue layers and affixed apical side down on cover slips coated with Cell-Tak [F. Wehner, L. Garretson, K. Dawson, Y. Segal, and L. Reuss. Am. J. Physiol. 258 (Cell Physiol. 27): C1159-C1164, 1990]. In 90% of the patches we observed K+ channels identical to the maxi-K+ channels previously demonstrated in the apical membrane (Y. Segal and L. Reuss. J. Gen. Physiol. 95: 791-818, 1990). To ascertain whether these channels were present in the native tissue, we carried out intracellular-microelectrode studies. We tested for activation of basolateral membrane K+ conductance by depolarization or by elevation of intracellular Ca2+ and for tetraethylammonium sensitivity of the basolateral membrane voltage and fractional resistance. The results were negative, indicating that maxi-K+ channels are not expressed in the basolateral membrane of the "intact" epithelium. Using the same intracellular-microelectrode protocol on the apical membrane, we demonstrated the presence of an apical K+ conductance attributable to maxi-K+ channels. Additional experiments revealed a Ba(2+)-sensitive basolateral K+ conductance in the native epithelium. We conclude that in the stripped preparation there is artifactual expression of maxi-K+ channels. In addition, the native basolateral membrane K+ channels either are not expressed in this preparation or have a low conductance and cannot be discerned from the background noise.


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 Proc. Natl. Acad. Sci. USAHome page
C. G. Vanoye and L. Reuss
Stretch-activated single K+ channels account for whole-cell currents elicited by swelling
PNAS, May 25, 1999; 96(11): 6511 - 6516.
[Abstract] [Full Text] [PDF]


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