Nitroglycerin Protects Small Intestine from Ischemia–Reperfusion Injury via NO–cGMP Pathway and Upregulation of α-CGRP

Abstract

IntroductionNitroglycerin (NTG) has been reported to possess preconditioning-like (PCL) protections on heart and other tissues. Our previous studies showed that NTG has acute PCL effects on rat small intestine. The present studies were designed to study whether NTG has delayed PCL protection on rat small intestine and to explore its mechanism(s). MethodsThe intestine lesions were evaluated by histologic examination and serum lactate dehydrogenase (LDH) measurement. The effects of nitric oxide (NO), cGMP, and α-calcitonin gene-related peptide (CGRP) synthesis on the effects of NTG were analyzed. ResultsPretreatment with NTG (0.12 mg/kg i.v.) 24 h before ischemia–reperfusion (I/R) of super mesenteric artery significantly reduced histologic lesions and serum LDH with elevated blood levels of NO and CGRP. Inhibition of guanylate cyclase by methylene blue (30 mg/kg i.p.) or specific depletion of transmitters in capsaicin-sensitive sensory nerve by capsaicin (50 mg/kg s.c.) abrogated the protection conferred by NTG. Reverse-transcription polymerase chain reaction analysis showed that NTG upregulates the expression of α-CGRP messenger RNA (mRNA), but not β-CGRP mRNA in lumbar dorsal root ganglia. ConclusionIn conclusion, NTG prevents rat small intestine from I/R injury by delayed PCL effects 24 h after administration. The protective effects are mediated by NO–cGMP pathway and α-CGRP upregulation.