Substrate concentration dependence of contraction characteristics in glycerinated horseshoe crab skeletal muscle fibres

Abstract

1. 1. The MgATP concentration dependence of isometric force, ATPase activity and unloaded shortening velocity was studied on glycerinated horseshoe crab muscle fibres. 2. 2. The isometric force and the ATPase activity reached their maxima at 10 −5 M MgATP and 10 - ̊ 4 M MgATP, respectively. 3. 3. The unloaded shortening velocity continued to increase with increasing MgATP concentration up to 3 × 10 3 M. 4. 4. The differences in MgATP concentration dependence of contraction characteristics between horseshoe crab and rabbit skeletal muscle fibres are discussed in relation to the current sliding filament hypothesis.