Effect of difluoromethylornithine on atrial natriuretic peptide in rat atria

Polyamines are aliphatic cations known to have a role in cellular growth and differentiation. In this study, difluoromethylornithine (DFMO), an inhibitor of polyamine synthesis, was used to investigate its effect on atrial natriuretic peptide (ANP) in atria of rat. The rats were given DFMO (2%) in drinking water for 10 days and three intraperitoneal administrations (200 mg/kg), 24, 18 and 1 h prior to experiment. Radioimmunoassay of ANP in atrial extracts indicated that DFMO treatment increased ANP contents of atria. ANP from atrial extracts was immunoprecipitated using ANP antibody and the immunoprecipitate was resolved and detected by SDS-PAGE and Western blotting. The predominant ANP peptide in both control and DFMO group migrated at 17 kDa. The synthesis of ANP was studied following the intravenous administration of [35S]methionine. ANP in atrial extracts was immunoprecipitated by ANP antibody. The incorporation of ANP into control and DFMO group peaked at 30 min and returned to a basal level by 60 min. DFMO decreased the incorporation of [35S]methionine into ANP. At 30 min following the administration of [35S]methionine, putrescine restored the synthesis of tricholoroprecipitable atrial proteins, but had no effect on the synthesis of ANP. At 60 min following, the amount of labeled ANP in DFMO + putrescine-treated group was significantly lower than that in DFMO group. These results indicate that polyamines influence both the synthesis and secretion of ANP.