Spermine or putrescine increased cAMP levels through a catalase-sensitive mechanism, resulting in, most notably, a dephosphorylation of protein A (M r 45 000, pI 5.15) and protein B (M r 45000, pI 4.9) and slightly increased phosphatidylcholine (PC) synthesis in HL60 cells. Exogenous dibutyryl cAMP mimicked the polyamine effects. 12-O-Tetradecanoyl phorbol-13-acetate (TPA) also promoted the protein dephosphorylation and PC synthesis, the effects augmented by R59022 and mimicked by exogenous 1-oleoyl-2-acetylglycerol. The effects of spermine (or dibutyryl cAMP) and TPA on PC synthesis were synergistic. It was suggested that cAMP-dependent protein kinase and protein kinase C might mediate, in an independent but interrelated manner, the effects of polyamines and TPA.
