Endogenous inhibitors of cyclic nucleotide phosphodiesterase: isolation and partial characterization

ABSTRACT

We have developed an extraction procedure to isolate from mammalian organs and cells endogenous factors that inhibit cyclic nucleotide phosphodiesterase [PDE]. The procedure involves homogenization of an organ or cell type in HC1 followed by extraction with chloroform methanol. The aqueous-methanol phase is separated and lyophilised. This material containing PDE inhibitor activity is further purified by gel filtration chromatography on Sephadex G-25 and G-75 columns. In rat and bovine brain, calf thymus, guinea pig lungs and ileum, human stomach, rat peritoneal mast cells and mouse splenic lymphocytes, cAMP and cGMP dependent PDE activity was inhibited in dose dependent fashion by the lyophilised material derived from these tissues. In other experiments the material from calf thymus selectively inhibited the PDE of calf thymus and not of any other tissue. Preliminary investigation of the physico-chemical properties of rat and bovine extracts indicated that brain contained inhibitory peptides of low molecular weight whereas calf thymus extracts contained inhibitory peptides of both low and high molecular weights. This method therefore reveals the presence of endogenous inhibitors of PDE [EIPODS] in various mammalian organs and cells