This Article Full Text Full Text (PDF) All Versions of this Article: 40/2/220    most recent 01.HYP.0000027134.14160.1Dv1 Alert me when this article is cited Alert me if a correction is posted Citation Map Services Email this article to a friend Similar articles in this journal Similar articles in PubMed Alert me to new issues of the journal Download to citation manager Request Permissions Citing Articles Citing Articles via HighWire Citing Articles via Google Scholar Google Scholar Articles by Parhami-Seren, B. Articles by Haupert, G. T. Search for Related Content PubMed PubMed Citation Articles by Parhami-Seren, B. Articles by Haupert, G. T., Jr Pubmed/NCBI databases Compound via MeSH Substance via MeSH Hazardous Substances DB OUABAIN Related Collections Other hypertension Hypertension - basic studies Ion channels/membrane transport Autonomic, reflex, and neurohumoral control of circulation Other Vascular biology

(Hypertension. 2002;40:220.)
© 2002 American Heart Association, Inc.

Scientific Contributions

Ouabain-Binding Protein(s) From Human Plasma

Behnaz Parhami-Seren; Richard Haberly; Michael N. Margolies; Garner T. Haupert, Jr

From the Department of Surgery (B.P.-S., M.N.M.) and Renal Unit (R.H., G.T.H.), Medical Services, Massachusetts General Hospital, Harvard Medical School, Boston, Mass.

Correspondence to Dr Garner T. Haupert, Jr, Renal Unit, CNY 8, Massachusetts General Hospital, Building 149, 13th Street, Charlestown, MA 02129. E-mail haupert.garner{at}mgh.harvard.edu

Conservation of the binding site on mammalian Na⁺,K⁺-ATPase for cardiac glycosides and the importance of the Na⁺ pump in mammalian cellular physiology has stimulated the search for a mammalian analog of these plant compounds. One candidate, isolated from brain and blood, appears to be ouabain itself or a closely related isomer, the ouabain-like compound. Little is known about the circulating form. Because human steroid hormones circulate with carrier proteins, we produced a ouabain-specific monoclonal antibody (mAb 1-10) and used it to probe normal human plasma for ouabain-protein carrier complex. Ouabain-like biological activity was isolated in association with protein bands of 80, 50, and 25 kDa. These proteins appear to be human immunoglobulins or immunoglobulin-like because they are recognized by anti-human immunoglobulin antibodies, but not by anti-mouse immunoglobulin antibodies. The protein-containing fractions inhibit the binding of mAb 1-10 to immobilized ouabain, and with further purification on protein A, the immunoglobulin-like protein binds radioactive ouabain with an IC₅₀ of 200 to 600 nmol/L, but binds digoxin with 100-fold less affinity, suggesting specificity for ouabain or its isomer. Active protein fractions after purification on C₁₈ inhibit Na⁺ pump activity in human erythrocytes (IC₅₀4 nmol/L, ouabain equivalents), and this chromatography appears to dissociate the ouabain-like compound from the immunoglobulin protein(s). These immunoglobulin-like molecules may represent a subset of immunoglobulins (0.5% of total protein A immunoglobulin) that function as a reservoir and delivery system for ouabain-like compounds in the modulation of human Na⁺, K⁺-ATPase in vivo.

Key Words: ouabain • digitalis-like factor • immunoglobulins • sodium pump

This article has been cited by other articles:

				A. Y. Bagrov, J. I. Shapiro, and O. V. Fedorova Endogenous Cardiotonic Steroids: Physiology, Pharmacology, and Novel Therapeutic Targets Pharmacol. Rev., March 1, 2009; 61(1): 9 - 38. [Abstract] [Full Text] [PDF]

				I. Dostanic-Larson, J. N. Lorenz, J. W. Van Huysse, J. C. Neumann, A. E. Moseley, and J. B Lingrel Physiological role of the {alpha}1- and {alpha}2-isoforms of the Na+-K+-ATPase and biological significance of their cardiac glycoside binding site Am J Physiol Regulatory Integrative Comp Physiol, March 1, 2006; 290(3): R524 - R528. [Abstract] [Full Text] [PDF]

				I. Dostanic-Larson, J. W. Van Huysse, J. N. Lorenz, and J. B Lingrel From The Cover: The highly conserved cardiac glycoside binding site of Na,K-ATPase plays a role in blood pressure regulation PNAS, November 1, 2005; 102(44): 15845 - 15850. [Abstract] [Full Text] [PDF]

				N. Bauer, J. Muller-Ehmsen, U. Kramer, N. Hambarchian, C. Zobel, R. H.G. Schwinger, H. Neu, U. Kirch, E.-G. Grunbaum, and W. Schoner Ouabain-Like Compound Changes Rapidly on Physical Exercise in Humans and Dogs: Effects of {beta}-Blockade and Angiotensin-Converting Enzyme Inhibition Hypertension, May 1, 2005; 45(5): 1024 - 1028. [Abstract] [Full Text] [PDF]

				H. M.A.M. Qazzaz, Z. Cao, D. D. Bolanowski, B. J. Clark, and R. Valdes Jr De Novo Biosynthesis and Radiolabeling of Mammalian Digitalis-Like Factors Clin. Chem., March 1, 2004; 50(3): 612 - 620. [Abstract] [Full Text] [PDF]