Effect of colchicine on mouse synovioblasts (B-cells)

The effect of colchicine on mouse synovioblasts (B-cells) was investigated by electron microscopy and electron microscopic morphometry with special consideration to intracellular movement and secretion of secretory granules. The volume density of microtubules decreased by one-fifth to one-tenth for 1-36 hr after colchicine administration, and that of secretory granules increased twofold for 3-24 hr. Secretory granules were accumulated around the Golgi apparatus for 3-6 hr, and in the cell periphery for 12-24 hr. Small vesicles positive for periodic acid-thiocarbohydrazide-silver proteinate stain were recognized beneath the plasma membrane for 12-24 hr. These results appear to indicate that intracellular translocation of secretory granules toward the plasma membrane is mediated by the microtubular system, and that most of their contents are released into the extracellular space via small vesicles.