Localization of Calcium-Accumulating Structures in Striated Muscle Fibers

Science  08 Jan 1965:
Vol. 147, Issue 3654, pp. 158-160
DOI: 10.1126/science.147.3654.158


When frog muscle fibers from which the sarcolemma had been dissected away were perfused with a calcium solution and then treated with oxalate, electron-opaque material, probably calcium oxalate, accumulated in the terminal sacs of the sarcoplasmic reticulum. These regions of calcium accumulation were identified with the intracellular calcium sink that controls the relaxation phase of the contraction-relaxation cycle; their proximity to tubules implicated in intracellular stimulus conduction suggests that they might also be regions from which calcium is released to trigger contraction.