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AJP - Cell Physiology, Vol 273, Issue 2 C434-C441, Copyright © 1997 by American Physiological Society
ARTICLES |
S. I. Helman and X. Liu
Department of Molecular and Integrative Physiology, University of Illinois at Urbana-Champaign 61801, USA.
A6 epithelia grown in tissue culture vary enormously in their baseline rates of Na+ transport due to differences in growth media, serum, and other unknown factors. To evaluate the effect(s) of substrates on expression of Na+ transport, we determined short-circuit currents, open-circuit voltages, and electrical resistances of mature confluent A6 epithelia grown on a variety of commercially available permeable supports. Because the cells, growth conditions, and all other factors were the same, differences in transport could be attributed alone to the substrate on which the cells were grown. Tissues were grown on both large- and small-diameter inserts of the same type with differing ratios of edge length to area so that the contribution of the edge and tight junction conductances to the combined shunt conductance of the inserts could be evaluated. Shunt and cellular conductances and the cellular Thevenin electromotive force were determined after aldosterone stimulation and amiloride inhibition of Na+ transport. Marked and extreme differences were observed not only for expression of Na+ transport (controls, 0.09-3.94 microA/cm2; aldosterone, 1.53-28.2 microA/cm2) due to changes of apical membrane conductance but also for the development of junctional conductances (3,250 to < infinity omega.cm2) and edge conductances (13,175 to < infinity omega.cm) among substrates.
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S. I. Helman, X. Liu, K. Baldwin, B. L. Blazer-Yost, and W. J. Els Time-dependent stimulation by aldosterone of blocker-sensitive ENaCs in A6 epithelia Am J Physiol Cell Physiol, April 1, 1998; 274(4): C947 - C957. [Abstract] [Full Text] [PDF] |
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L. M. Baxendale-Cox, R. L. Duncan, X. Liu, K. Baldwin, W. J. Els, and S. I. Helman Steroid hormone-dependent expression of blockersensitive ENaCs in apical membranes of A6 epithelia Am J Physiol Cell Physiol, November 1, 1997; 273(5): C1650 - C1656. [Abstract] [Full Text] [PDF] |
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