| The first part: the variation of the expression of lung PAI-1 in rats under different mechanical ventilation conditionsObjective: To observe the variation of the expression of lung PAI-1 in rats under different mechanical ventilation conditions.Methods: To clean 72 adult male SD rats, weighing 250~300g, which are divided into four groups, Group C, S, R and L according to random number table(n=18): control group(group C, spontaneous breathing group), low tidal volume group(group S, VT=6ml/kg), conventional tidal volume group(group R, VT=10ml/kg), large tidal volume group(group L, VT=40ml/kg), Each group is randomly divided into three subgroups(n=6) according to the duration of mechanical ventilation(2h, 4h, 6h). Rats in group S, R and L are taken small animal ventilators to support with mechanical ventilation after processing tracheotomy tube, Ventilator parameters are set to RR 70 beats/min, Fi O2 21%, PEEP 0 cm H2 O. The rats are killed instantly after the end of the experiment, cut open chest rapidly and taken out of right lung tissue, determining wet weight/dry weight ratio(W/D) after weighing, measuring the rate of apoptosis in lung tissue(TUNEL method), and scoring on lung injury under light microscope after the lung tissue is stained by HE. Comparing with the expression lung PAI-1 in rats under the condition of different tidal volume and different mechanical ventilation time. At the same time, To collect rat bronchoalveolar lavage fluid(BALT), measure the expression of PAI-1 and IL-8. Real-time PCR technology is applied to detect PAI-1m RNA expression of rat’s lung tissue.Results: Comparing with group C, the lung tissue of rats in group L diffused and existed bleeding points under light microscope after ventilating 2 hours. A lot of scattered bleeding points could be seen in lung tissue after ventilating 4 hours, alveolar septum was widened, alveolar cavity drainage was increased, the structures of lung tissue of rats in group L were damaged severely after ventilating 6 hours, little intact alveolar tissue was seen under light microscope, lung tissue function was lost mostly. Lung injury score、lung weight/dry weight ratio(W/D) and apoptosis index of lung tissue were increased significantly with prolonged ventilation time, the difference was statistically significant(P<0.05). Comparing with group C and group S, obvious lung injury performance didn’t appear in group S after mechanical ventilation for 6 hours. Comparing with group C, there was no obvious lung injury performance about lung tissue morphology in group R after mechanical ventilation for 2 hours or 4 hours, mild alveolar exudate can be seen under light microscope after ventilating 6 hours, but lung tissue structure is normal. Comparing with group C, the expression of lung PAI-1, IL-8 and PAI-1 m RNA of rats in group L were increased gradually with prolonged ventilation time(P<0.05). Comparing with the three time points(2h,4h,6h) in group S and R, To measure the expression of PAI-1、IL-8 and PAI-1 m RNA in group L after mechanical ventilation for 2 hours, the expression was up-regulated obviously at the time point 4h, the expression turned to the peak point at the time point 6h. The difference was statistically significant(P<0.05). Above indexes in group C and S showed no significant difference.Comparing with group C, the expression of lung PAI-1, IL-8 and PAI-1 m RNA in group R was not seen at the time point 2h and 4h, little expression of PAI-1 could be seen at the same time point 6h.Comparing with group C and group S with the different time points,2h, 4h and 6h, the expression of lung PAI-1, IL-8 and PAI-1 m RNA in group S was not up-regulated, the difference was not statistically significant(P>0.05). Little expression of lung PAI-1, IL-8 and PAI-1 m RNA in group R could be seen at the same time point 6h.The expression of lung PAI-1、IL-8 and PAI-1 m RNA of rats in group L at 3 time points(2h,4h,6h) were increased significantly with prolonged ventilation time, the difference was statistically significant(P<0.05).Conclusion: Large tidal volume mechanical ventilation could induce up-regulation of PAI-1 expression rats in rat lung tissue and bronchoalveolar lavage fluid. The expression of lung PAI-1 could be measured after ventilating 2 hours, the expression of lung PAI-1 was significantly up-regulated after ventilating 4 hours, the expression of lung PAI-1 turned to the peak point after ventilating 6 hours.The second part: the effect of different pretreatments on the expression of lung PAI-1 in rats after mechanical ventilationObjective: To discuss the effect of low tidal volume mechanical ventilation and sevoflurane pretreatment on the expression of lung PAI-1、IL-8 and PAI-1 m RNA in rats after mechanical ventilation and the relationships with lung injury.Methods: To clean 18 adult male SD rats, weighing 250~300g, which are divided into three groups according to random number table(n=6): group L(large tidal volume ventilation group, VT=40ml/kg); group P1(sevoflurane pretreatment group, 2% sevoflurane), Group P2(mechanical ventilation pretreatment group, VT =6ml/kg). Rats in group P1 are sucked into 2% sevoflurane preconditioning before large tidal volume ventilation for 30 minutes. Rats in group P2 are given mechanical ventilation pretreatment for 30 minutes(VT=6ml/kg).Rats in group P1 and P2 are given mechanical ventilation(VT=40ml/kg) when the pretreatment is over. Rats in group L、 P1 and P2 are taken small animal ventilators to support with mechanical ventilation for 4 hours after processing tracheotomy tube, ventilator parameters are set to RR=70 beats/min, Fi O2 21%, PEEP O cm H20. Rats are killed by intravenous injection after the end of mechanical ventilation. To collect right lung tissue, determine lung wet weight/dry weight ratio(W/D) and measure apoptosis index of lung tissue and score on lung injury under light microscope after the lung tissue is stained by HE. To collect bronchoalveolar lavage fluids of rats and measure the expression of lung PAI-1 and IL-8. The application of Real-time PCR can test the expression of lung PAI-1m RNA in rats.Results: Lung morphology in group L changed under light microscope, lung alveolar membrane was thickened obviously, a lot of bleeding points were diffused and existed in lungs, lung alveolars were fused, lung tissue structure in group P1 was basically complete, alveolar exudate was seen obviously. Alveolar wall in group P2 was thickened, but without the formation of hyaline membrane, lung tissue structure was intact. Comparing with group L, the differences of lung injury score、lung wet weight/dry weight ratio(W/D) and apoptosis index of lung tissue were not statistically significant comparing with group P1 and P2(P>0.05). Comparing with group L, the expression of lung PAI-1, IL-8 and PAI-1 m RNA in group P1 and P2 bronchoalveolar lavage fluid(BALF) was decreased significantly, the difference was statistically significant(P<0.05). Comparing with group P2 and P1, the differences of the expression of lung PAI-1, IL-8 and PAI-1 m RNA in bronchoalveolar lavage fluid(BALF) were not statistically(P<0.05).Conclusion: Large tidal volume and prolonged mechanical ventilation time induce high expression of PAI-1 in rats. Low tidal volume mechanical ventilation and sevoflurane pretreatment make the expression of rats’ lung PAI-1、IL-8 and PAI-1 m RNA down-regulated after mechanical ventilation.It is necessary to pay attention to PAI-1 may be associated with lung injure induced by mechanical ventilation, low tidal volume and sevoflurane may have a protective effect on lung injury, the mechanism needs to be further studied. |
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