Length-tension relation in limulus striated muscle

Abstract

Laser diffraction techniques coupled with simultaneous tension measurements were used to determine the length-tension relation in intact, small (0.5-mm thick, 1.0-mm wide, 20- 25-mm long) bundles of a Limulus (horseshoe crab) striated muscle, the telson levator muscle. This muscle differs from the model vertebrate systems in that the thick filaments are not of a constant length, but shorten from 4.9 to ≈2.0 µm as the sarcomeres shorten from 7 to 3 µm. In the Limulus muscle, the length-tension relation plateaued to an average maximum tension of 0.34 N/mm2 at a sarcomere length of 6.5 , um (Lo) to 8.0 ttm. In the sarcomere length range from 3.8 to 12.5 ttm, the muscle developed 50% or more of the maximum tension. When the sarcomere lengths are normalized (expressed as L/Lo) and the Limulus data are compared to those from frog muscle, it is apparent that Limulus muscle develops tension over a relatively greater range of sarcomere lengths. © 1980, Rockefeller University Press., All rights reserved.