Subcellular distribution of sodium pump isoform subunits in
mammalian cardiac myocytes.
McDonough, Alicia A., Yibin Zhang, Victoria Shin, and Joy S. Frank.
Department of Physiology and Biophysics, University of Southern
California School of Medicine, and Departments of Medicine and
Physiology, University of California at Los Angeles School of
Medicine
APStracts 2:0377C, 1995.
The cardiac sodium pump (Na,K-ATPase) provides the driving force for
the Na+-Ca++ exchanger, a determinant of intracellular Ca++ stores.
Three sodium pump [alpha] catalytic subunit isoforms are expressed in
human heart, [alpha]1 and [alpha]2 in rat heart and only [alpha]1 in
guinea pig heart. The objective of this study was to determine
whether there are isoform specific patterns of expression in the
transverse tubules (T-tubules) versus the peripheral sarcolemma (SL).
In adult rat cardiomyocytes anti-[alpha]1 specific antibodies labeled
the T-tubules more intensely than the peripheral SL where labeling
was patchy, the same pattern reported for distribution of the Na+
-Ca++ exchanger (Frank et al, J. Cell Biol.,1992), while anti [alpha]2
and anti [beta]1 antibodies uniformly labeled T-tubules and
peripheral SL. In guinea pig cardiomyocytes an anti-[alpha] antibody
against an extracellular epitope evenly labeled the peripheral SL, T
-tubules, and immunogold labeling demonstrated coincidence of [alpha]
subunits and intramembranous particles in sarcolemma. In summary,
sodium pumps are located in both peripheral sarcolemma and transverse
tubules of cardiomyocytes expressing either multiple or single sodium
pump isoforms.
Received 8 August 1995; accepted in final form 6 October 1995.
APS Manuscript Number C491-5.
Article publication pending Am. J. Physiol. (Cell Physiology).
ISSN 1080-4757 Copyright 1995 The American Physiological Society.
Published in APStracts on 6 November 95