[Causes of the preferential action of imuran on the viability and proliferative activity of a Chinese hamster cell culture in the stationary growth phase].

It has been shown that the active principle of imuran, 6-mercaptopurine, exerts a similar though less pronounced effect on viability and proliferative activity of Chinese hamster cells by affecting them preferentially in the stationary phase of growth. This effect cannot be attributed to the inhibition by imuran of xanthine oxidase, as proposed earlier, since another inhibitor of this enzyme, allopurinol, appears more effective, causing more cell deaths during exponential growth phase rather than during stationary growth. Other possible grounds for different cytotoxic effects of imuran depending upon the proliferative status of a cell have been discussed.