Molecular basis for cellular effects of naturally occurring polyamines

The naturally occurring polyamines, putrescine, spermidine and spermine, and the analogue cadaverine, induce a dose-dependent histamine release from rat peritoneal mast cells. Spermine was the most active among these polycationic metabolites, followed by spermidine and putrescine. The histamine release was inhibited by a 2 h pretreatment of the cells with pertussis toxin (100 ng/ml), demonstrating the involvement of a pertussis toxin-sensitive GTP-binding regulatory protein during the exocytotic process. Experiments performed with purified Go/Gi proteins reconstituted into phospholipid vesicles showed a direct stimulation of GTPase activity by the polyamines. This direct stimulation of G proteins and the consequent activation of the coupled effectors may represent a new mechanism of action for natural polyamines controlling receptor-dependent processes.