In Chaos chaos streaming, motility, and cytokinesis were inhibited nearly 100% for several hours by 2.5–5 mM sodium adenosine triphosphate (ATP)1 added to culture fluid. All three effects were completely prevented by the addition of equimolar Mg++ or Ca++ ions but not Na+ to the ATP/culture fluid solution. The effects of ATP were not reproduced by EDTA, EGTA, colchicine, or AMP. Sodium pyrophosphate produced about 50% inhibition at 5 mM. Studies with 14C-ATP showed that 5 x 10-5 to 5 x 10-4 mmole of ATP was firmly associated with each milliliter of packed cells after an hour's incubation at 24°C. Labeling studies also showed that prevention of the ATP effects by Mg++ ions was not due to a decrease in the amount of ATP associated with the cells.

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