Journal of Applied Physiology, Vol 76, Issue 1 253-258, Copyright © 1994 by American Physiological Society

ARTICLES

A modified force-velocity equation for smooth muscle contraction

J. Wang, H. Jiang and N. L. Stephens
Department of Physiology, Faculty of Medicine, University of Manitoba, Winnipeg, Canada.

It has been suggested that in skeletal muscle the force-velocity relationship may not be a simple hyperbolic one, as defined by Hill's equation. To determine whether smooth muscle demonstrated the same properties, quick-release force-velocity curves were obtained from canine tracheal smooth muscle. The results showed that the observed data points for tracheal smooth muscle systematically deviated from a hyperbola. Such deviation occurred at values of force (P) approaching maximum isometric force (Po) for curves elicited by quick release at 2 and 10 s in the course of isometric contractions. Shortening velocities under a given afterload were overestimated at the high-force end (P > 75% Po) by Hill's equation; this implied that a relationship more complex than a simple hyperbola was involved at high loads. We next focused on finding an equation to also fit those directly measured data points that did not conform to a hyperbola. Our rationale in developing the equation was that a plot of the linearized transform of Hill's equation should yield a straight line over the entire range of loads at which velocities were measured. The plot demonstrated that, in the low-load high-velocity portion of the curve, a peak value was reached at 70-80% Po, which decreased as load increased in the high-load low-velocity portion.(ABSTRACT TRUNCATED AT 250 WORDS)

This article has been cited by other articles:

				P. Chitano, L. Wang, S. N. Mason, R. L. Auten, E. N. Potts, W. M. Foster, A. Sturrock, T. P. Kennedy, J. R. Hoidal, and T. M. Murphy Airway smooth muscle relaxation is impaired in mice lacking the p47phox subunit of NAD(P)H oxidase Am J Physiol Lung Cell Mol Physiol, January 1, 2008; 294(1): L139 - L148. [Abstract] [Full Text] [PDF]

				F-X. Blanc, C. Coirault, S. Salmeron, D. Chemla, and Y. Lecarpentier Mechanics and crossbridge kinetics of tracheal smooth muscle in two inbred rat strains Eur. Respir. J., August 1, 2003; 22(2): 227 - 234. [Abstract] [Full Text] [PDF]

				C.-L. Que, C. M. Kenyon, R. Olivenstein, P. T. Macklem, and G. N. Maksym Homeokinesis and short-term variability of human airway caliber J Appl Physiol, September 1, 2001; 91(3): 1131 - 1141. [Abstract] [Full Text] [PDF]

				P. Chitano, J. Wang, C. M. Cox, N. L. Stephens, and T. M. Murphy Different ontogeny of rate of force generation and shortening velocity in guinea pig trachealis J Appl Physiol, April 1, 2000; 88(4): 1338 - 1345. [Abstract] [Full Text] [PDF]

				C.-L. QUE, G. MAKSYM, and P. T. MACKLEM Deciphering the Homeokinetic Code of Airway Smooth Muscle Am. J. Respir. Crit. Care Med., March 1, 2000; 161(3): S161 - 163. [Full Text] [PDF]

				S. P. Driska, R. E. Laudadio, M. R. Wolfson, and T. H. Shaffer A method for isolating adult and neonatal airway smooth muscle cells and measuring shortening velocity J Appl Physiol, January 1, 1999; 86(1): 427 - 435. [Abstract] [Full Text] [PDF]