Calcium-induced calcium release mechanism from the sarcoplasmic reticulum in skinned crab muscle fibres.

Mechanically skinned skeletal muscle fibres of the crab Carcinus maenas have been used to investigate the mechanism of calcium release from the sarcoplasmic reticulum. Calcium release has been monitored by the amplitude and kinetics of the tension developed by the fibre. Results show that a very low calcium concentration, insufficient to directly activate contractile proteins, induces a release of calcium from the SR. This release is stimulated by low concentrations of caffeine and inhibited by small amounts of EGTA. Thus, a graded calcium-induced calcium release mechanism dependent on extrareticular calcium concentration has been demonstrated in skinned crab muscle fibre.