Journal of Muscle Research & Cell Motility

, Volume 24, Issue 1, pp 15–32

Cardiotonic bipyridine amrinone slows myosin-induced actin filament sliding at saturating [MgATP]

  • J. Klinth
  • A. Arner
  • A. Månsson
Article

DOI: 10.1023/A:1024894130989

Cite this article as:
Klinth, J., Arner, A. & Månsson, A. J Muscle Res Cell Motil (2003) 24: 15. doi:10.1023/A:1024894130989

Abstract

Previously reported effects of amrinone on skeletal muscle function suggest that the drug reduces the rate constant of myosin cross-bridge dissociation. We have used the in vitro motility assay to further elucidate the mechanism underlying this effect and to aid these studies a new, improved, filament tracking software was developed in the Matlab™ environment. The experiments were carried out at 30°C using heavy meromyosin from fast rabbit muscle and rhodamine–phalloidin labeled actin filaments. A slowing effect of amrinone on filament sliding velocity at 1mM MgATP was observed at drug concentrations >0.3 mM. This effect showed signs of saturation at the highest drug concentrations (1–2 mM) that could be readily tested. The sliding velocity exhibited hyperbolic dependence on [MgATP] with a Vmax of 7.2 ± 0.9 μm/s and a KM of 0.18 ± 0.02 mM. Amrinone (1 mM) reduced Vmax by 32 ± 5% (P < 0.01) and KM by 42 ± 8% (P < 0.05; n = 4). These results are accounted for in the most straightforward way by a model where amrinone acts directly on the actomyosin system and reduces the rate constant of MgADP release. Such a well-defined effect on the myosin cross-bridge cycle makes the drug a potentially useful pharmacological tool for further studies of myosin function both in vitro and in the ordered filament array of a living muscle fiber.

Copyright information

© Kluwer Academic Publishers 2003

Authors and Affiliations

  • J. Klinth
    • 1
  • A. Arner
    • 2
  • A. Månsson
    • 1
  1. 1.Department of Chemistry and Biomedical SciencesUniversity of KalmarKalmarSweden
  2. 2.Department of Physiological SciencesUniversity of LundLundSweden