Ciliary but not saltatory movements are inhibited by vanadate microinjected into living cultured cells.

Abstract

To test the idea that saltatory organelle movements of nonmuscle cells might be driven by microtubule-dynein interactions, we microinjected vanadate into several different types of cultured cell. Solutions of sodium metavanadate made up in a simple buffered salt solution were pressure microinjected into fully spread cells in an open-topped culture chamber placed on the stage of an inverted microscope. The cells were observed by oil-immersion phase-contrast optics and results were recorded on movie film. Vanadate, at 10(-5)-10(-2) M, microinjected into cultured chick embryo fibroblasts, failed to inhibit organelle movements. To test the effectiveness of vanadate's inhibitory action under living cell conditions, ciliated epithelial cells were microinjected. In these cells even the smallest microinjection of 5 X 10(-5) M vanadate caused an immediate cessation of ciliary beating. Moreover, in cells that were well spread it was found that whereas vanadate, at 5 X 10(-5)-5 X 10(-3) M, inhibited ciliary motion, it failed to inhibit organelle saltations in the same cell. To determine whether vanadate would inhibit a living actin-myosin system, myocardial cells were also microinjected. Following microinjection of 5 X 10(-5) and 5 X 10(-4) M vanadate a temporary tonic contraction (which also occurred following microinjection of buffer alone) was followed by regular beating. Taken together these results demonstrate that in living cell systems microtubule-dynein interactions are as sensitive to vanadate inhibition as they are in demembranated model systems, and that a working actin-myosin system in a living muscle cell does not share this great sensitivity. In light of the pronounced differential inhibitory effects of vanadate on the movements of cilia and organelles, our results suggest that saltatory organelle movements in chick embryo fibroblasts and rabbit oviduct epithelial cells are unlikely to be brought about by microtubule-dynein interactions.