Whole-cell sodium conductance of principal cells freshly isolated from rat cortical collecting duct. Bubien, James K. Department of Medicine/Division of Nephrology, Nephrology Research and Training Center, University of Alabama at Birmingham, The Department of Veterans Affairs Medical Center, Birmingham, Alabama 35294
APStracts 2:0160C, 1995.
Cortical collecting duct fragments were manually dissected from 6 week old Sprague-Dawley rats. The fragments were enzymatically digested (collagenase A) into single cells, washed, and resuspended in serum -free RPMI-1640. Individual cells were examined electrophysiologically using the whole-cell patch clamp technique. Two morphologically distinct cell types were present in the cell suspension. Small round cells which had a capacitance of 7 pF and larger oval cells with a capacitance of 29 pF were consistently observed. Whole-cell electrophysiological examination revealed that the small round cells had virtually no plasma membrane ionic conductance, while both inward and outward currents were observed in the larger oval type cells. Also, superfusion of 250 pM arginine-vasopressin specifically increased the inward conductance of only the larger cells. The effect could be completely inhibited by 2 [mu]M amiloride or 100 [mu]M Rp -CPT-cAMP (a specific cyclic AMP inhibitor). These findings are consistent with the hypothesis that the larger cells are principal cells and the smaller cells are intercalated cells, and directly demonstrate that an amiloride-sensitive whole-cell conductance is readily observable in freshly isolated cortical collecting duct cells. Thus, the whole-cell configuration of the patch clamp technique appears to be well suited for assessing cellular mechanisms that regulate the ionic conductances of cortical collecting duct cells. 

Received 6 June 1994; accepted in final form 29 March 1995.
APS Manuscript Number C303-4.
Article publication pending Am. J. Physiol. (Cell Physiology).
ISSN 1080-4757 Copyright 1995 The American Physiological Society.
Published in APStracts on 10 April 1995.