AJP - Cell Physiology, Vol 253, Issue 6 C862-C865, Copyright © 1987 by American Physiological Society
Isozymes of dog heart Na+-K+-ATPase are immunologically similar to isozymes in brain
A. A. McDonough and C. A. Schmitt
Department of Physiology and Biophysics, University of Southern California School of Medicine, Los Angeles 90033.
The sodium pump, Na+-K+-ATPase, possesses two populations of cardiac
glycoside-binding sites in cardiac tissue. This has been observed in other
tissues such as brain where the two sites have been assigned to isozymes of
Na+-K+-ATPase termed alpha and alpha +. In a previous study [Am. J.
Physiol. 248 (Cell Physiol. 17): C247-C251, 1985], we were unable to
demonstrate the presence of an alpha +-form in guinea pig heart sarcolemmal
membranes using antibody probes. In the present study, using similar
methodology, we show that dog, but not rat or guinea pig, sarcolemmal
membranes contain two immunologically distinct alpha-subunits. The
antibody-binding characteristics of dog heart alpha and alpha + are similar
to the forms found in brain. The relative abundance of the two isozymes,
estimated by labeling the sarcolemmal membranes with fluorescein
5'-isothiocyanate, was about equal. We conclude that the two populations of
ouabain-binding sites in dog heart may result, at least in part, from the
presence of the two isozymes of Na+-K+-ATPase in cardiac tissue of this
species.
