Sarcoplasmic Reticulum: Ultrastructure of the Triadic Junction

Science  12 Mar 1965:
Vol. 147, Issue 3663, pp. 1308-1310
DOI: 10.1126/science.147.3663.1308


The appositional region between the intermediate element and adjacent cisternae in the triads of the sarcoplasmic reticulum of striated muscle from humans, copepods, ostracods, and barnacles shows a five-layered construction similar to that of a tight junction. Known functions of tight junctions and cisternal elements suggest that a membrane depolarization, conducted by the intermediate element, is transmitted to the cisternae by way of the triadic junction to cause a release of calcium ions from the cisternae.