Effect of 5‘-deoxy-5’-isobutylthioadenosine on putrescine uptake and polyamine biosynthesis by chick embryo fibroblasts

Abstract
The effect of 5''-deoxy-5''-S-isobutylthioadenosine (SIBA) on polyamine biosynthesis was studied by using cultured chick embryo fibroblasts. The drug inhibits the uptake of [14C]putrescine and its conversion into labeled spermidine or spermine. The inhibitory effect is reversed by removing the inhibitor after exposing the cells to the drug for 24 h. SIBA also caused a significant decrease in cellular spermine levels and an accumulation of putrescine. These changes are reversed by removing the inhibitor. SIBA had the same effect on chick embryo fibroblasts transformed by Rous sarcoma virus; a decrease in cellular spermine levels in SIBA-treated cells was observed. In all the experiments SIBA caused a reduction in the spermine/putrescine and spermidine/putrescine ratios. SIBA an inhibitor of transmethylation and it also interferes with polyamine biosynthesis, probably by blocking aminopropyltransferase.