Effect of the Physical Training on the Vascular Responsiveness after Pulmonary Ischemia/Reperfusion in Rat

Abstract

Ischemia/reperfusion (IR) process is a pathological condition which causes serious cell and tissue lesions, mainly on the endothelial cells. Although the effect of the gastrointestinal and heart IR has been largely studied, few studies have addressed the effect of pulmonary IR on the vascular responsiveness. Furthermore, no studies exist to investigate the effect of exercise training on the vascular responsiveness after pulmonary IR process. PURPOSE: the aim of this study was to evaluate the effect of physical training on the reactivity of pulmonary artery rings from rats submitted to a pulmonary IR. METHODS: Wistar male rats were divided into five groups named: control sedentary (SD); Trained (TR); sham operated (SHAM); IR sedentary (IR/SD) and IR trained (IR/TR). Run training (RT) was performed for 5 days/week, each session of 60 min, during 8 weeks at intensity of 66% of VO2max. After RT, animals from IR groups were submitted to a pulmonary IR for 90 min and reperfusion for 2 hours. Rats were sacrificed and the pulmonary artery rings were isolated. Concentration-response curves to acetylcholine (ACh), sodium nitroprusside (SNP), phenylephrine (PHE) and tromboxane A2 analogue (U46619) were obtained. The potency and maximal response (Emax) were determined. RESUlTS: Body weight at initial time was similar in all groups (213±2.7 g) whereas the body weight after 8 weeks of study was 397±4 and 350±6.5 g in SD and TR groups, respectively. Neither the potency nor the Emax in rat pulmonary artery were modified for ACh (SD: 6.64±0.1; TR: 6.72±0.03; SD/IR: 6.91±0.01; SHAM:6.94±0.06, IR/TR: 6.94±0.04) and U46619 (SD: 7.52±0.07; TR:7.18±0.09; SD/IR: 7.26±0.3; SHAM: 6.96±0.06; IR/TR: 7.10±0.05) in all groups. On the other hand, a significant increased in potency for SNP were found in TR groups, about of 4-fold (8.21±0.02 and 8.29±0.1 for TR and IR/TR groups, respectively) in comparison with Control groups (SD: 7.6±0.1; SHAM: 7.76±0.15; IR/SD: 7.83±0.03). No changes on the Emax for SNP were seen. The potency for PHE was decreased in IR/SD (6.98±0.2); TR (7.01±0.13); and IR/TR (6.71±0.2) groups as compared to SD group (7.93±0.1). The Emax for PHE in pulmonary artery rings were not modified in all groups. CONCLUSIONS: Our findings show that RT improved the endothelium-independent relaxing response for SNP that was not affected by pulmonary IR. On the other hand, the contractile response evoked by PHE was reduced either in RT or IR groups.