Cytochalasin B stabilises the sub-cortical actin bundles of Chara against a solution of low ionic strength.

The properties of the sub-cortical actin bundles in the perfused Chara cell model are altered by concentrations of cytochalasin B (CB) which inhibit streaming. This is demonstrated by treating the bundles with intracellularly introduced CB after first using ATP to strip away their associated motile organelles. Such CB-treated bundles are resistant to a solution of low ionic strength which, as judged by light and electron microscopy, extracts untreated bundles. It is therefore concluded that a site of action for CB lies within the actin bundles and that, while the alteration detected may not itself be of direct physiological significance, it may nonetheless indicate the site at which CB inhibits streaming in both the cell model and the intact cell.