Up-regulation of substance P in the lungs during acute myocardial ischemia and infarction in rats

Abstract

Objective Previous studies indicate that disturbance of respiratory functions during acute myocardial ischemia and infarction was not always parallel with decline of cardiac functions, indicating that some non-hemodynamic mechanism might be underlying the changes in the lungs. Methods The current study was designed to investigate the changes in the expression of substance P and its mRNA in the lungs and dorsal root ganglia using assays of immunohistochemistry, enzyme immunoassay, in situ hybridization and real-time quantitative reverse transcription-polymerase chain reaction, with a rodent model of acute myocardial infarction induced by permanent coronary artery occlusion, without and with epidural anesthesia in the upper thoracic segments of the spinal cord. Results Marked up-regulation of substance P in the lungs and the dorsal root ganglia of upper thoracic segments (T1–T5) was detected at 15, 30, 60, 180 and 360 min of coronary artery occlusion. The peptide was observed in the alveolar epithelium, mainly in type II pneumocytes, epithelium of bronchiole and the vascular walls. The preprotachykinin mRNA was mainly observed in the dendrites of nerve cells in the alveolar wall, the bronchiole and the pulmonary vessels and the basal lamina of the bronchiole. Pre-treatment of the animals with epidural local anesthetic could completely abolish the up-regulation of SP in the lungs and the dorsal root ganglia. Conclusions The findings may suggest the involvement of substance P in the pathology of cross-talk between the heart and lungs in acute myocardial ischemia and infarction. Neural mechanism may be involved in the up-regulation of substance P in the lungs.