Voltage dependence of depolarization-contraction coupling processes in skeletal muscle cells

Changes of contraction and optical anisotropy of isolated skeletal muscle cells from Rana temporaria and Astacus fluviatilis were compared under voltage clamp conditions. The time course of the optical signal from frog muscle was shown to consist of two components which could be attributed to calcium binding both on the sarcoplasmic reticulum Ca-ATPase and troponin C. The optical signal from the crayfish muscle has no distinguishable components, and its onset probably reflects the start of Ca-ATPase activity. This hypothesis is supported by the analysis of effects of some pharmacological agents and conditioning depolarization on tension and optical signal.