Metabolic support of na+-pump in apically permeabilized a6 kidney
cell epithelia: role of creatine kinase.
Guerrero, Maria Lourdes, J[diaeresis]org Beron, Benjamin Spindler,
Peter Groscurth, Theo Wallimann, and Fran[cedilla]cois Verrey.
Institute of Physiology and Institute of Anatomy, University of
Z[umlaut]urich, Winterthurerstrasse 190, CH-8057 Zurich, Institue for
Cell Biology, Swiss Federal Institute of Technology, ETH
-H[diaeresis]onggerberg, CH-8093 Zurich, Switzerland
APStracts 3:0291C, 1996.
The contribution of ATP generating systems to Na+-pump (Na+,K+-ATPase)
function was studied in Xenopus laevis A6 kidney epithelia apically
permeabilized with digitonin. The ouabain-inhibitable Na+-pump
current (IP) was measured in the presence of otherwise impermeant
inhibitors and/or substrates at Na+ and K+ concentrations allowing
near maximal pump function. Confocal fluorescence microscopy after
apical addition of sulfosuccinimidobiotin (M.W. 443) showed that all
cells were permeabilized. Less than 15% of the endogenous lactate
dehydrogenase (LDH) and creatine kinase (CK) were released into the
apical medium. The IP was 5 [mu]A/cm2 in the presence of D-glucose.
Blocking glycolysis with 2-deoxy-D-glucose or oxidative
phosphorylation with antimycin A decreased it by >/=50%. Exogenously
added ATP prevented these decreases fully or partially, respectively.
Two CK isoforms were detected, one being likely mitochondrial the
other corresponding to mammalian B-CK. Phosphocreatine (PCr)
partially restored Na+-pump activity during inhibition of either ATP
synthesis pathway. In conclusion, the ATP used by Na+-pumps of
apically digitonin-permeabilized A6 epithelia is generated to a
similar extent by glycolysis and oxidative phosphorylation. The CK
system can partially support the ATP supply to the Na+-pumps.
Received 20 June 1996; accepted in final form 6 September 1996.
APS Manuscript Number C353-6.
Article publication pending Am. J. Physiol. (Cell Physiology).
ISSN 1080-4757 Copyright 1996 The American Physiological Society.
Published in APStracts on 7 October 1996