VELOCITY OF FREE SHORTENING AND ELASTICITY IN GLYCERINATED MOLLUSCAN SMOOTH-MUSCLE

1. 1. Velocity of free shortening (V0) and elasticity of the glycerinated anterior byssal retractor muscle (ABRM) of Mytilus were examined by applying length steps during contractions at pCa 6.3 and 6.5. 2. 2. The highest V0 obtained during the rise of active force at pCa 6.3 was 0.77 L0/sec at 20°C, the value comparable to that in frog twitch fibers if expressed as the sliding velocity between thick and thin filaments. 3. 3. The amount of elastic shortening required to reduce an active force to zero level was less than 2% of the fiber length, which was greater than that estimated by extrapolating back the shortening curve to the time of the length step. © 1990.