Aim
: To examine gastric mucosal ulcerogenic responses to indomethacin and HCl/ethanol in adjuvant arthritic (AA) rats.
Methods and Results
: Arthritis was induced in male Dark Agouti (DA) rats by injection of Freund's complete adjuvant (FCA) into the right hind paw. The gastric ulcerogenic response to indomethacin was markedly worsened in AA rats, depending on the degree of arthritic change. This aggravation of indomethacin‐induced gastric lesions in AA rats was significantly prevented by NG‐nitro‐L‐arginine methyl ester (L‐NAME) and amino‐guanidine as well as dexamethasone. In contrast, the mucosal ulcerogenic response to HCl/ethanol was inhibited in AA rats. The suppression of HCl/ethanol‐induced gastric lesions in AA rats was reversed almost totally by L‐NAME and aminoguanidine as well as dexamethasone and partly by indomethacin. The expression of inducible nitric oxide synthase (iNOS) mRNA was observed in the stomach of AA rats but not of normal rats. Moreover, the luminal releases of nitric oxide (NO) metabolites as well as prostaglandin (PG) E2 were significantly increased in AA rats.
Conclusions
: The gastric mucosal ulcerogenic responses were modified in AA rats, in different manners depending on the irritants; an increase in response to indomethacin and a decrease in response to HCl/ethanol. These changes may both be accounted for by increased production of NO by iNOS, and the latter is also partly related to increased production of PGs.
We conclude that pantoprazole exhibited both anti-ulcer and healing promoting effects on duodenal ulcers in rats, and the effects may be attributable to its potent anti-secretory action. Other pump inhibitors such as omeprazole and lansoprazole were almost equally effective as pantoprazole, yet this drug was most potent on the basis of ED50 values.
We examined gastric acid secretion in response to various stimuli in streptozotocin (STZ) induced diabetic rats and characterized the alteration of acid secretory responses in diabetic conditions. Animals were injected STZ (70 mg/kg, intraperitoneally) and used after five weeks of diabetes with blood glucose >350 mg/dl. Under urethane anesthesia, the experiment was performed in a chambered stomach or a whole stomach preparation, and the acid secretion was measured at pH 7.0 using a pH-stat method and by adding 100 mM NaOH. The acid secretion was stimulated by intravenous infusion of either histamine (4 mg/kg/hr), pentagastrin (60 microg/kg/hr), or carbachol (20 microg/kg/hr) or by intraluminal application of peptone solution (4%), or vagal electrical stimulation (2 msec, 3 Hz, 0.5 mA). In normal rats, acid secretion was increased in response to either histamine, pentagastrin, carbachol, peptone, or electrical vagal stimulation. In STZ diabetic rats, however, changes in acid secretion varied depending on the stimuli; the acid response to histamine remained unchanged, but the responses to vagal electrical stimulation or pentagastrin and carbachol were significantly decreased or enhanced, respectively, as compared to normal rats. Likewise, the acid response to peptone was also markedly enhanced in STZ-diabetic rats, and this response was significantly blocked by atropine and YM022 (a CCKB/gastrin antagonist) as well as famotidine in both normal and diabetic rats. Both pentagastrin and carbachol increased the luminal release of histamine in normal rats, and these responses were significantly augmented in STZ-diabetic rats. The altered acid response and histamine release induced by pentagastrin in STZ diabetic rats were partially reversed by daily injection of insulin. These results suggest that STZ-diabetic rats showed different changes in gastric acid secretion in response to various stimuli. The increased acid secretory response may be associated with an enhanced release of mucosal histamine, while the decreased response may be due to vagal neuropathy.
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