Intestinal ischemia following thermal injury can cause structural and functional damages in the intestinal epithelium. Patients, especially children may develop enteropathy after burn injury. Our study showed that Na+/glucose cotransport in the small intestine, measured in Ussing chambers, was reduced 30 min after a 40% total body surface area (TBSA) burn. The reduction was still detectable at 48 hr after burn. Differentiation of stem cells into mature epithelial cells is important in restoring physiological functions in the gut after injury. Retinoic acid receptors(RARs), especially RAR-β play an important role in promoting epithelial differentiation. However, there are reports that RAR-β is not expressed in the small intestine of normal rats. To explore the possibility of restoring burn-induced damage of epithelial functions by retinoids, we examined the expression of retinoic acid nuclear receptors in jejunal and ileal mucosa from rats received burn injury. Mucosa of jejunum and ileum was collected at 2,4,24,48, and 72 hr after a 40% TBSA burn and total RNA was isolated. The expression of RAR mRNA was determined using reverse transcriptase polymerase chain reaction technique. Expression of RAR-γ, a constitutively expressed RAR, was detected in all mucosal samples, and was not affected by thermal injury. RAR-β mRNA was detected in ileal mucosa collected at 72 hr after burn and was not detectable in other mucosal samples from rats received either burn or sham procedure. Conclusion: 1) RARγ is constitutively expressed in the small intestine, 2) RAR-β is not expressed in the small intestine of normal rats, and 3) RAR-β expression is induced in the ileum 72 hr after burn.
