Comparison of the antisecretory and antiucler activity of epidermal growth factor, urogastrone and transforming growth factor alpha and its derivative in rodents in vivo

This study investigates the effects of epidermal growth factor (EGF), urogastrone (UG) and transforming growth factor-alpha (TGFα) and its derivative on dimaprit- and pentagastrin-induced gastric acid secretion and on acidified ethanol (AE)-evoked ulcer formation in anaesthetized rats. EGF, TGFα and UG administered subcutaneously (s.c.) 30 min before dimaprit inhibited gastric acid secretion. Against pentagastrin-stimulated secretion, TGFα inhibited, while EGF and UG potentiated, acid secretion dose-dependently. Intraduodenal (i.d.) administration of TGFα and UG had no effect, while EGF potentiated, both secretagogue-induced acid secretion in the same dosage schedule. Administration of either EGF, UG or TGFα i.v. bolus, in response to continuous infusion of dimaprit resulted in a significant (p < 0.05-p < 0.001) inhibition of acid secretion which was transient and returned to normal within 30-45 min for UG while it slowly returned to normal for EGF and TGFα. The truncated form of TGFα (amino acids 34-43) did not show any antisecretory effect when administered parenterally. Acidified ethanol produced gastric haemorrhagic lesions in the rat 1 h after oral administration. The gastric mucosal protective effects of TGFα, EGF and UG administered either orally or s.c. 30 min before the administration of AE were dose-dependent against this model of ulcer induction. Indomethacin (Indo), administered 15 min before AE to inhibit prostanoids biosynthesis, significantly (p < 0.001) reduced the cytoprotective effects of TGFα, EGF and UG and aggravated the ulcer index when administered s.c. The results show that PGs may be involved in mediating the protective effects of the three growth factors. Administration of NG-nitro-L argininemethylester (L-NAME) 15 min prior to TGFα, EGF and UG s.c. or orally, significantly (p < 0.001) decreased the degree of ulcer indices and was able to reduce the protective effects of TGFα, EGF and UG, thus including the role of NO in mediating the protective effects of these growth factors. In conclusion, these results have demonstrated that EGF, UG and TGFα have a short and reversible inhibitory effect on dimaprit-stimulated gastric acid secretion and each is effective parenterally but not orally. UG and EGF potentiated, while, TGFα inhibited pentagastrin-stimulated acid secretion. In addition, TGFα seems to lose its activity when it is truncated from the C terminus. The present study also suggests that EGF, UG and TGFα are equally effective against AE-induced gastric ulcer and bring about their cytoprotective action through their reduction of acid secretion and through PG and NO pathways.