| OBJECTIVE:To study the protective effects of prostavasin on lung ischemia-reperfusion injury. METHODS:Clean Sprague-Dawley rats(220-280g body wt) were anesthetized with an intraperitoneal injection of 1% sodium Phenobarbital (30-50mg/Kg body wt),intubated after tracheotomy and ventilated with room air under the following conditions:respiratory rate of 70 breathes/min,peak airway pressure of 2cm H2O and a ratio of inspiratory to expiratory duration of 1 to 2 during surgery.A left anterolateral thoracotomy in the fifth intercostal space was performed.Left lung hilus were isolated atraumatically.Animals received 50IU of heparin intravenously(iv) in saline (total volume 500ul).Fives minutes after heparin was administered, left pulmonary artery,vein and bronchus were temporarily clamped for 60 minutes with non-crushing microvascular clamp.During the experiment,the lung was kept moist with periodic application of warm normal saline and the incision was covered to minimize evaporative losses.The period of ischemia was constant at 60 minutes.At the end of the ischemic period the clamp was removed from the hilum and the lung was allowed to ventilate and reperfuse.Animals were administered 0.5ml of warm subcutaneous saline per hour to maitain hydration during experiment.At the end of the reperfusion period,a min-line incision from the neck to the pubis was made to allow access to the chest .Blood samples were obtained from the inferior vena cava just before killing.The lung separated from the heart and mediastinal tissues and then analyzed as outlined in what follows.Time-matched sham control animals underwent the same procedure ,except the microvascular clamp was not applied to the lung hilum.Treated animals received 10ug/kg iv of prostavasin 5min before reperfusion. Seventy-five rats were randomly divided into three groups:S group(n=25):thoractomy was performed without clamping left hilus and prostavasin therapy;P group(n=25):treated with 10ug/kg prostavasin in five minutes before reperfusing.and IR group(n=25):left ling hilus were clamped for 60 minutes and then reperfused without prostavasin therpy.Five rats were put to death at one of five time points(60min after ischemia ,30min,90min,120min and 240min after reperfusion) in each group after blood was collected from the heart and then discarded the left lung.The TNF-αconcentration in plasma,the wet/dry(W/D) ratio and the contents myeloperoxidase in lung tissue were determined and lung tissue histopathological changes were determined by the microscope,each group P-selectin protein were assayed by immnuhistochemitery. RESULTS: (1) The TNF-αconcentration in plasma:in IR group TNF-αwas increased obviously at 30min,90min,120min and 240min after reperfusion and it was significantly higher than that in the S group and P group in the same time point(p<0.05).The increase of TNF-αwas meaningless in the P group after reperfusion. (2):The contents of MPO in lung tissue :MPO in the IR group was significantly higher in each same time point after ischemia-reperfusion than that in both the S group and P group (p<0.05),MPO in the P group was higher after reperfusion ,but the increased level of MPO in the P group was obviously less than that in the S group(p<0.05). (3):The MDA concentration in plasma:The MDA concentration in plasma were increasing after reperfusion in IR group and P group ,and the degree of MDA increase in the IR group was obviously higher than that in the P group and S group(p<0.05) .the increase of the MDA in the P group after reperfusion was insignificant,when compared with that in the S group. (4):The W/D ratio of lung tissue:After ischemia-reperfusion ,the W/D in the IR group and P group were increasing progressively and reached the highest at 240min after reperfusion;the degree of W/D increase in the P group was obviously less than that in the IR group(p<0.05). (5):The level of P-selectin in the lung tissue:In the S group the expression of P-selectin was smaller ,but the obvious increase of the expression P-selectin was found in the IRgroup;Compared with that in the IR group,the expression of P-selectin in the P group was obviously smaller(p<0.05) . (6)Histologic evaluation:in the process of ischemia-reperfusion the lung injury was aggravating progressively in the IR group ;there was marked pulmonary capillary congestion ,interstitial adema and intraalveolar hemorthage,exfiltration.The pulmonary pathologic alterations occurred to a lesser degree in the P group compared with the IR group. CONCLUTIONS: 1. "The lung ischemia-reperfusion injury model "was established successfully in the rats,and the mechanism of lung ischemia-reperfusion injury may have close relationship with cytokinin released increasingly the increase of oxygen free radicals,following to neutrophils aggregating and activating in lungs after reperfusion,and the increase of the expression P-selectin after reperfusing. 2. The MPO assay was used to quantitate tissue neutrophil accumulation in the lung,in a sense it acts as a parameter to evaluate the level of lung tissue injury. 3. Prostavasin could be used to protect lung ischemia-reperfusion injury, it could decrease cytokinin releasing and oxygen free radicals generation ,inhibit neutrophils aggregating and activating in the lungs, thereby inhibiting expression of P-selectin.
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