Cyclooxygenase-1 and an alternatively spliced mRNA in the rat stomach: effects of aging and ulcers

Prostaglandins play a critical role in gastric mucosal cytoprotection and d ecrease progressively with age. Cyclooxygenase (COX), the rate-limiting enz yme for prostaglandin synthesis, exists in two isoforms, COX-1 and COX-2. T he rat COX-1 gene expresses an alternatively spliced mRNA COX-1 splice vari ant (SV) that may, at best, code for a truncated COX-1 protein. With the us e of competitive PCR, we determined whether COX gene expression was altered in the stomach with increasing age and after gastric ulcer induction. COX- I, mRNA was significantly reduced in the aged, and COX-1SV mRNA was signifi cantly higher in the adults compared with the young and aged stomach. Level s of COX-1 and COX-2 were similarly expressed in the normal stomach. In acu te gastric ulcers, only COX-2 mRNA levels were significantly elevated. When ulcers were undergoing healing and repair, COX-1 and COX-2 mRNA levels wer e significantly elevated. Age-related changes in COX-I and COX-1SV but not COX-2 mRNA may alter gastric mucosal cytoprotection. Furthermore, COX-1 and COX-2 may both contribute to the healing of a gastric ulcer.