Vanadate affects nuclear division and induces aberrantly-shaped cells during subsequent cytokinesis in Tetrahymena

Sodium orthovanadate at 0.1-5.0 mM affected cell proliferation of Tetrahymena in a dose-dependent manner. At 1 h the cell increment was 76-12% of the control (100%), but after lag periods in 1-5 mM the growth rate remained at 76% of control in 0.1 mM vanadate and at 64-61% of control in 0.2-5.0 mM vanadate. Endocytosis was affected in both a time- and dose-dependent manner; an increasing number of cells did not form vacuoles. Cell motility increased initially in 0.1 mM vanadate but decreased later as it did in 0.5-2.0 mM vanadate where the proportion of immobile cells increased with time. Cell divisions occurred at all concentrations but macronuclear elongation was disturbed and subsequent cytokinesis resulted in daughter cells containing the entire G2 macronucleus, a large or small portion of it, or no nucleus at all. Moreover, odd cell shapes appeared with time. The size of the cell and nucleus increased but there was great variation with disturbed cytoplasm/nucleus ratios. Treated cells had dilated rough endoplasmic reticulum that included dense material, presumed to be vanadate, which was not seen in control cells. Scant amounts of dense material were found in dense granules, small vacuoles, and abundantly in contractile vacuoles. It is argued that interference with proper microtubular function is the main effect of vanadate.