Canavanine, diaminopropane, α-methylornithine and methylglyoxal bis(guanylhydrazone) decreased the intracellular polyamine concentrations in growing baby hamster kidney cells. Each of the inhibitors also prevented polyamine efflux into the extracellular medium. Concomitant with the decrease in polyamine excretion was a change in the distribution of polyamines in the extracellular medium. In each case there was a decrease in the amount of radioactivity present as free spermidine and an increase in that found as acetyl polyamines. The magnitude of this shift correlated with the degree of inhibition of excretion. It may be that acetyl polyamines play a role in the regulation of polyamine excretion.
