Adverse effects of vagotomy on ethanol-induced gastric injury in the rat. Absence of a role for glutathione redox cycle

Influence of ethanol-metabolising systems on intensity of lipid peroxidation processes in gastrointestinal tract of rats

The effects of some ethanol-metabolising systems (aldehyde dehydrogenase, catalase, cytochrome P450 2E1) on activation of lipid peroxidation (LPO) processes in gastrointestinal tract of rats have been studied using inhibitors of these systems. The intensity of LPO processes was evaluated by thiobarbituric acid-reactive products and chemiluminiscence intensity. It was found, that the acetadehyde metabolism play the main role in the indiction of lipid peroxidation in the gastrointestinal tract of rats.

Intracisternal PYY increases gastric mucosal resistance: role of cholinergic, CGRP, and NO pathways

The influence of intracisternal injection of peptide YY (PYY) on gastric lesions induced by ethanol was studied in urethan-anesthetized rats. Gastric lesions covered 15-22% of the corpus as monitored 1 h after intragastric administration of 45% ethanol (5 ml/kg) in intracisternal vehicle control groups. PYY, at doses of 23, 47, or 117 pmol 30 min before ethanol, decreased gastric lesions by 27%, 63%, and 59%, respectively. Thyrotropin-releasing hormone (TRH) receptor antisense oligodeoxynucleotide pretreatment (intracisternally, 48 and 24 h before intracisternal PYY) did not influence the gastroprotective effect of intracisternal PYY (47 pmol) but abolished that of intracisternal TRH analog RX-77368 (4 pmol). RX-77368 (2.6 pmol) and PYY (6 pmol) were ineffective when injected intracisternally alone but reduced ethanol lesions by 44% when injected simultaneously. Atropine (subcutaneously), the calcitonin gene-related peptide (CGRP) receptor antagonist CGRP-(8-37) (intravenously), or the nitric oxide (NO) synthase inhibitor N(G)-nitro-L-arginine methyl ester (L-NAME, intravenously) completely abolished the gastroprotective effect of intracisternal PYY (47 pmol), whereas indomethacin (intraperitoneally) had no effect. The L-NAME action was reversed by L-arginine but not by D-arginine (intravenously). These results suggest that intracisternal PYY acts independently of medullary TRH to decrease ethanol-induced gastric lesions. The PYY action involves vagal cholinergic-mediated CGRP/NO protective mechanisms.

Medullary thyrotropin-releasing hormone mediates vagal-dependent adaptive gastric protection induced by mild acid in rats

BACKGROUND & AIMS

Adaptive gastric protection is dependent on vagal pathways in rats. It is hypothesized that medullary thyrotropin-releasing hormone (TRH), known to regulate vagal function, is part of the brain mechanisms mediating adaptive gastric protection.

METHODS

Urethane-anesthetized rats were pretreated with either acute bilateral subdiaphragmatic vagotomy, sham operation, or intracisternal injection of purified control, TRH, or peptide YY antibody. Gastric lesions were assessed 75 minutes after orogastric administration of 1 mL of either vehicle or 0.35N HCl followed 15 minutes later by 0.6N or 1.0N HCl.

RESULTS

Injection of 0.6N and 1.0N HCl induced gastric lesions covering 23.1% +/- 2.7% and 37.8% +/- 3.3% of the corpus mucosa, respectively. Pretreatment with 0.35N HCl resulted in 67.3% and 50.5% reductions in gastric lesions induced by 0.6N and 1.0N HCl, respectively. Subdiaphragmatic vagotomy or intracisternal injection of TRH antibody increased gastric lesions induced by 0.6N HCl to 32.2% +/- 2.2% and 42.9% +/- 5.6%, respectively, and completely abolished the protective effect of 0.35N HCl pretreatment. Control or peptide YY antibody injected intracisternally did not alter the gastric protection induced by mild acid.

CONCLUSIONS

These results indicate that medullary TRH plays a role in the vagally mediated adaptive gastric protection induced by mild acid.