Ornithine decarboxylase and polyamine biosynthesis in pancreatic adaptation.

Abstract

This study was designed to investigate the role of ornithine decarboxylase (ODC) and polyamines in pancreatic adaptation. Cholecystokinin (CCK) is well-known to be a potent trophic stimulus on the pancreas. On the other hand, the oral application of the synthetic trypsin inhibitor camostate results in an extensive release of endogenous CCK in rats. alpha-difluoromethylornithine (DFMO), an irreversible and specific inhibitor of ODC, was applied simultaneously to elucidate the essential role of polyamines in pancreatic growth. Camostate feeding (200 mg/kg b.wt. orally twice a day) resulted in a rapid elevation of ODC activity already after 2 hours, reaching a maximum after 6 hours (about 200fold above controls) followed by a significant increase in putrescine after 4 hours and spermidine after 24 hours while spermine remained unchanged. The trophic parameters increased as expected in following time-course: thymidine kinase (12 hours), DNA polymerase (12 hours), protein (24 hours), pancreatic weight (24 hours) and DNA (5 days). DFMO (2% in drinking water + 3 x 300 mg/kg b.wt. i.p. during daytime) was not able to prevent but significantly delayed and reduced the camostate-induced increase in ODC and polyamines as well as the trophic parameters. These data indicate an essential role for ODC and polyamines in camostate-induced pancreatic growth and hormonal mediated pancreatic adaptation.