Journal of Applied Physiology, Vol 67, Issue 6 2447-2453, Copyright © 1989 by American Physiological Society

ARTICLES

Phosphorylation of rodent cardiac myosin light chain 2: effects of exercise

D. P. Fitzsimons, P. W. Bodell and K. M. Baldwin
Department of Physiology and Biophysics, University of California, Irvine 92717.

The purpose of this study was to ascertain whether the degree of cardiac myosin light chain 2 (P-light chain) phosphorylation occurs as a function of changes in cardiovascular functional state as induced by 1) treadmill exercise (20-27 m/min, 0% grade for 20, 30, 45 min) (phase I) and 2) pharmacological intervention (phase II) in adult female Sprague-Dawley rats. It was hypothesized that cardiac myosin phosphorylation is regulated in accordance with time-dependent sustained elevations in myocardial work demands requiring alterations in either heart rate or left ventricular pressure development. Exercise heart rates (HR) and double products (HR x DP) were equivalent among the three exercise groups and were significantly elevated in comparison with the normal-rest (NR) group (P less than 0.05). In phase II, isoproterenol elicited higher HR, although the atenolol group exhibited a marked reduction in HR, mean arterial pressure, and double product relative to NR (P less than 0.05). Percent myosin P-light chain phosphorylation exhibited both a HR- and a work load-dependent modulation in P-light chain levels (-9% to +23% change) in the two phases of the study (P less than 0.05). These data are consistent with the view that the above responses are associated with modulations in intracellular calcium concentrations commensurate with the alterations in HR and left ventricular pressure. Also, elevations in P-light chain phosphorylation could serve to augment left ventricular pressure development under these functional states.

This article has been cited by other articles:

				R. R. Lamberts, N. Hamdani, T. W. Soekhoe, N. M. Boontje, R. Zaremba, L. A. Walker, P. P. de Tombe, J. van der Velden, and G. J. M. Stienen Frequency-dependent myofilament Ca2+ desensitization in failing rat myocardium J. Physiol., July 15, 2007; 582(2): 695 - 709. [Abstract] [Full Text] [PDF]

				M. C. Olsson, J. R. Patel, D. P. Fitzsimons, J. W. Walker, and R. L. Moss Basal myosin light chain phosphorylation is a determinant of Ca2+ sensitivity of force and activation dependence of the kinetics of myocardial force development Am J Physiol Heart Circ Physiol, December 1, 2004; 287(6): H2712 - H2718. [Abstract] [Full Text] [PDF]

				C. Bozzo, L. Stevens, L. Toniolo, Y. Mounier, and C. Reggiani Increased phosphorylation of myosin light chain associated with slow-to-fast transition in rat soleus Am J Physiol Cell Physiol, September 1, 2003; 285(3): C575 - C583. [Abstract] [Full Text] [PDF]

				R. Vandenboom and J. M. Metzger A "Wringing" Endorsement for Myosin Phosphorylation in the Heart Mol. Interv., November 1, 2002; 2(7): 422 - 424. [Abstract] [Full Text] [PDF]

				N. Suematsu, S. Satoh, S. Kinugawa, H. Tsutsui, S. Hayashidani, R. Nakamura, K. Egashira, N. Makino, and A. Takeshita {alpha}1-Adrenoceptor-Gq-RhoA signaling is upregulated to increase myofibrillar Ca2+ sensitivity in failing hearts Am J Physiol Heart Circ Physiol, August 1, 2001; 281(2): H637 - H646. [Abstract] [Full Text] [PDF]

				A. Sanbe, J. G. Fewell, J. Gulick, H. Osinska, J. Lorenz, D. G. Hall, L. A. Murray, T. R. Kimball, S. A. Witt, and J. Robbins Abnormal Cardiac Structure and Function in Mice Expressing Nonphosphorylatable Cardiac Regulatory Myosin Light Chain 2 J. Biol. Chem., July 23, 1999; 274(30): 21085 - 21094. [Abstract] [Full Text] [PDF]