Regulation of Diamine Oxidase Expression by Ornithine Decarboxylase in Isolated Rat Small Bowel Enterocytes

Ornithine decarboxylase (ODC) and diamine oxidase (DAO), enzymes involved in polyamine metabolism, are highly expressed by small bowel enterocytes. Modulation of ODC expression is mediated through cellular concentration of polyamines that inhibits the enzyme synthesis and also induces the synthesis of an inhibitory protein, the antizyme, which in turn binds to ODC and inhibits its activity. DAO is an important regulator of intracellular concentration of polyamines because it catalyzes the degradation of putrescine into gamma-aminobutyraldehyde. Change in intracellular polyamine concentration has been suggested to represent a regulatory factor for DAO expression. In order to investigate a possible regulation of DAO expression by ODC, we studied the effect of difluoromethylornithine (DFMO), a selective, irreversible inhibitor of ODC, on DAO activity in isolated rat small bowel enterocytes. Our data demonstrate that in isolated small bowel enterocytes ODC inhibition by 10 mM DFMO reduced DAO activity by 53%, suggesting that, in our experimental conditions, ODC plays a regulatory role on DAO expression.