Abstract
A possible link between the corticoid-elicited premature expression of intestinal sucrase-isomaltase (SI) and endogenous changes in polyamine metabolism was investigated in preweaned rats. Starvation at postnatal day 12 caused a precocious expression of SI mRNA and activity. A rapid upsurge of serum corticosterone was observed during the first hour of isolation, occurring in parallel with a transient enhancement of ornithine decarboxylase (ODC) expression and followed by an increase in mucosal polyamine content. Administration of the antiglucocorticoid RU-38486 completely prevented the starvation-evoked stimulation of ODC. The treatment of the sucklings with RU-38486 or with alpha-difluoromethylornithine (DFMO), a specific inhibitor of ODC, dramatically reduced the amount of SI mRNA. When exogenous hydrocortisone (HC) was administered to 12-day-old sucklings nourished by their dam, an important accumulation of ODC mRNA was observed in the intestinal mucosa 4 h after treatment. Sucklings receiving HC and treated concomitantly with either RU-38486 or DFMO exhibited a reduced amount of ODC mRNA and a dramatic decline in both SI mRNA and activity. Altogether these data support the view that the premature induction of SI expression is dependent on changes in ODC expression and polyamine metabolism that can be elicited either by endogenous changes or by exogenously administered glucocorticoids.
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