Role of polyamine biosynthesis during gut mucosal adaptation after burn injury

The induction of ornithine decarboxylase (ODC) mRNA and of ODC enzyme activity are important events in gut repair after cutaneous burn injury. ODC catalyzes the rate-limiting step in the biosynthesis of polyamines that are necessary for normal cell growth; α-difluoromethylornithine (DFMO) specifically inhibits ODC activity. The purpose of this study was to examine the role of polyamines in the adaptive response of gut mucosa after burn injury. In experiment 1, male Sprague-Dawley rats (250 to 300 g; n=6/group) were randomized into sham, 60% burn, or 60% burn plus DFMO. In experiment 2, rats with either a 60% burn or 60% burn plus DFMO treatment received spermidine by gavage. We measured ODC activity, polyamine levels, and DNA content at 0, 12, 24, and 48 hours postburn in the mucosa of both the proximal and distal small intestine. Burn injury produced early atrophy (by 12 hours postburn) of the gut mucosa characterized by decreased mucosal weight and DNA content. Increased ODC activity and polyamine content in both the proximal and distal gut mucosa of burned rats preceded restoration of mucosal weight and DNA content that occurred at 48 hours postburn; these responses were prevented by DFMO treatment. Spermidine administration failed to accelerate gut mucosal recovery after burn injury alone, but oral administration of spermidine reversed the inhibitory action of DFMO on gut mucosal repair. These data suggest that the early increases of gut ODC activity and polyamine levels after burn injury are crucial cellular events for the repair of subsequent gut mucosa.