Luminal polyamines substitute for tissue polyamines in duodenal mucosal repair after stress in rats

The purpose of this study was to examine whether luminal polyamines administered exogenously accelerate the repair of stress-induced intestinal mucosal damage in rats. Rats were fasted for 22 hours, placed in restraint cages, and immersed in water to the xiphoid process for 6 hours. Animals were killed either immediately after the period of stress or at 4, 12, and 24 hours thereafter. Duodenal mucosa was examined histologically, and ornithine decarboxylase activity and polyamine levels were measured. Repair of duodenal mucosa after stress was extensively delayed by administering 500 mg/kg DL-alpha-difluoromethylornithine (DFMO) IP. DFMO also inhibited ornithine decarboxylase activity and prevented increases in duodenal mucosal polyamine content. Intragastric administration of the polyamines, putrescine, spermidine, and spermine (100 mg/kg), immediately after stress significantly prevented the decreased rate of repair caused by DFMO. Spermidine or spermine accelerated healing better than putrescine in the DFMO-treated rats. Spermine also significantly increased the normal rate of repair of stress-induced damage. The delayed recovery of mucosal DNA, RNA, and protein content following stress in the DFMO-treated rats was prevented by exogenous polyamines. The reduced levels of duodenal mucosal spermidine and spermine in stressed rats treated with DFMO returned toward control levels after administration of exogenous spermidine. These results indicate that (a) luminal polyamines effectively substitute for endogenously synthesized polyamines in the repair process of the duodenal mucosa, (b) luminal polyamines can increase the normal healing rate and, (c) polyamines accelerate healing by increasing both an early phase and a later phase dependent on cell renewal.