Ontogeny of apical membrane ion conductances and channel expression
in cortical collecting duct cells.
Huber, Stephan M., and Michael F. Horster.
Physiologisches Institut, UniversitSt M[diaeresis]ynchen, D- 80336
M[diaeresis]ynchen, Federal Republic of Germany
APStracts 3:0111F, 1996.
Ontogeny of apico-basolateral epithelial cell polarity was studied by
a comparison of embryonic ureteric bud (UB) and mature cortical
collecting duct (CCD) primary cultures. Patch clamp techniques were
applied to identify apical ion channels and to measure specific
conductance (nS/10pF) of the apical membrane (ga) and of the whole
cell (Gw ). In UB, Gw (1.3 +/- 0.17; n=32) and ga (1.4 +/- 0.15; n=9)
were not different, while they differed greatly in CCD (Gw: 0.79 +/-
0.07; n=35; ga: 2.3 +/- 0.38; n=9). In UB, DIDS (100 [mu]M) reduced
ga and Gw similarly by 0.66 +/- 0.21 (n=9) and 0.48 +/- 0.07 (n=7),
respectively, whereas DIDS had no effect in CCD. Amiloride (1 mM) did
not alter UB conductance while in CCD ga was more reduced than Gw
(0.75 +/- 0.18; n=8 versus 0.22 +/- 0.10; n=7). In addition to this
Na+-selective conductance, a non-selective cation (NSC) conductance
was enriched sixfold in the apical membrane of CCD, possibly due to
apical 9 +/- 1 pS (n=7) NSC channels, while UB apical NSC conductance
was low. Apical 16 +/- 2 pS (n=6) K+ channels were identified in CCD
but not in UB. The comparison of both developmental states suggests a
differentiation of the apical membrane during UB to CCD ontogeny.
Received 13 October 1995; accepted in final form 30 May 1996.
APS Manuscript Number F348-5.
Article publication pending Am. J. Physiol. (Renal Fluid Electrolyte
Physiology).
ISSN 1080-4757 Copyright 1996 The American Physiological Society.
Published in APStracts on 4 July 96