REGULATION OF THE INDUCTION OF ORNITHINE DECARBOXYLASE IN SHORT-TERM RAT COLON ORGAN-CULTURE BY DEXAMETHASONE AND 13-HYDROXYOCTADECADIENOIC ACID (13-HODE)

The activity of rat colon mucosal ornithine decarboxylase (ODC) was found to dramatically increase within three hours after placement of mucosal explants under organ culture conditions. Increases of 224-fold above the initial levels were observed 24 hours after establishment of cultures. During the next 72 hours, activity gradually declined although it never reached in vivo levels. Inclusion of either dexamethasone (DEX) or 13-hydroxyoctadecadienoic acid (13-HODE) in the media suppressed the early induction of ODC activity but did not abolish the increases. The effect of these compounds was reversible. Within 24 hours after removal of either dexamethasone or 13-HODE the ODC activity increased to the level found in untreated control cultures. These data suggest that glucocorticoids and 13-HODE may play a role in the regulation of colonic cellular proliferative activities in intact animals. The findings with 13-HODE add to the growing list of examples of regulation of biological activity by oxidized derivatives of linoleic acid.