Role of polyamines in the stimulation of synthesis and secretion of plasminogen activator from bovine aortic endothelial cells

The effects of the polyamines putrescine (PUT), spermidine (SPD), and spermine (SPM) on the secretion of plasminogen activator (PA) and plasminogen activator inhibitor (PAI) were evaluated using cultured bovine aortic endothelial cells. All three polyamines enhanced PA secretion in a time‐ and dose‐dependent manner, with a potency rank order of SPM > SPD > PUT. The PA stimulation required both RNA and protein synthesis, as evidenced by inhibition of polyamine‐induced PA secretion by actinomycin D and cycloheximide. The inhibitors of polyamine biosynthesis methylglyoxal bis‐(guanylhydrazone) (MGBG) and dl‐(difluoromethyl) ornithine (DFMO) alone did not affect basal or polyamine‐induced PA secretion, with the exception that MGBG reduced the effect of PUT. Polyamine‐treated cells enhanced secretions of both tissue‐type and urokinase‐type PA. The results of the present study suggest that polyamines may play a role in the regulation of PA synthesis and secretion and that this function can be modified under pathophysiological conditions affecting cellular and tissue levels of polyamines.