Calcium-containing granules in myoepithelial cells of the polychaete Syllis spongiphila: possible ionic modulators

Myoepithelial cells of the polychaete Syllis spongiphila have a central core containing abundant membrane-bound granules. Examination of isolated and in situ granules using radioactive labelling, X-ray energy dispersive spectrometry, and scanning and transmission electron microscopy indicated that the granules contain high levels of Ca and P, and take up free Ca ions with a time course of 15-30 min. The granules appear to contribute to the dynamic calcium metabolism of the myoepithelial cells.