Effect of monoclonal antibody against the new ouabain receptor protein (31.5 kD) on contractile responses and Ca-transients in cardiac muscle

• Published in: Japanese Journal of Pharmacology 1994, Vol.64 (suppl.1), p.99-99
• Main Authors: Fujino, Sumiko, Fujino, Masako
• Format: Article
• Language: eng ; jpn
• ISSN: 0021-5198
• DOI: 10.1016/S0021-5198(19)50040-3

We have already reported that a new ouabain receptor protein (NORP), which has a high affinity for ouabain and is independent of (Na^+ -K^+ ) ATPase, was solubilized from transverse tubule membrane-junctional SR complexes in cardiac muscles. To clarify the mechanism of ouabain potentiation, we examined the role of this protein in cardiac functions with special reference to the excitation-contraction (E-C) coupling process. Electrically stimulated kitten papillary muscles which had been previously loaded with fura 2 were immersed in a Tyrode solution containing the monoclonal antibody (MoAB) for 60 min and then washed out. Twenty min after the MoAB-removal, both twitch- and K- contracture tensions were still inhibited (about 50 %), but resting- and action-potentials and caffeine contracture were unchanged. Ca-transients during twitch and K-contracture were inhibited (abut 50 %), but Ca-transients during caffeine contracture were not. Ouabain (0.5 μM) selectively accelerated E-C coupling and increased Ca-transients, by both about 50 %. Results suggest that MoAB and ouabain influence E-C coupling and Ca-transients by binding to NORP.