RELATION OF ORNITHINE DECARBOXYLASE AND TYROSINE KINASE-ACTIVITY IN THE JEJUNAL MUCOSA IN-VIVO

Our aim was to study the relationship between jejunal mucosal activity of ornithine decarboxylase and tyrosine kinase during proliferation i n adolescent rats in vivo, Their relationship in the proliferating int estinal mucosa under in vivo conditions has not been reported before, From the results of in vitro studies, it was speculated that tyrosine kinase activity modulated ornithine decarboxylase activity during colo nic mucosal proliferation (Majumdar AP, Am J Physiol 259:G626-G630, 19 90), Jejunal mucosal hyperplasia was induced by Type I diabetes and su ppressed in both control and diabetic rats by administration of difluo romethylornithine. Jejunal mucosal weight and enzyme activity were det ermined after 3, 6, and 10 days, and tyrosine-specific phosphorylated proteins after 10 days of induction of diabetes, Difluoromethylornithi ne suppressed jejunal mucosal proliferation and tyrosine kinase activi ty after the 6- and 10-day study periods, After the 3-day study period although jejunal mucosal growth was suppressed, tyrosine kinase activ ity was not, Activity of tyrosine kinase and ornithine decarboxylase w ere highly significantly correlated at all time periods in both contro l and diabetic rats, Tyrosine-specific phosphorylated proteins of 34, 54, 80, and 200 kDa proteins were observed in jejunal mucosa of both c ontrol and diabetic rats, In the difluoromethylornithine-treated rats, phosphorylation of the above proteins was negligible while the phosph orylation of a 14-kDa protein was prominent, We speculate that in vivo ornithine decarboxylase activity may be modulating tyrosine kinase ac tivity and that phosphorylation of a 14-kDa protein was associated wit h suppressed mucosal growth in difluoromethylornithine-treated rats.