Change in expression of macrophage migration inhibitory factor mRNA in a rat model of ventilator-induced lung injury

Objective To investigate the changes in the expression of macrophage migration inhibitory factor （MIF） mRNA in a rat model of ventilator-induced lung injury. Methods Thirty adult male Sprague-Dawley rats, weighing 235-260 g, were randomly divided into 3 groups （ n = 10 each） using a random number table： con- trol group （group C）, small tidal volume （VT ） mechanical ventilation group （group S） and large tidal volume me- chanical ventilation group （group L） . The animals were anesthetized with intraperitoneal ketamine 100 mg/kg, mi- dazolam 0.2 mg/kg and atropine 1.0 mg/kg. The rats were tracheostomized and spontaneous breathing was main- tained in group C, while the rats were tracheostomized and mechanically ventilated for 4 h in groups S and L. The tidal volume was 7 ml/kg （group S） or 40 ml/kg （group L）,I： E was 1 ： 1, RR was 80 bpm and FiO2 was 100% . At 4 h of spontaneous breathing or mechanical ventilation, broncho-alveolar lung lavage fluid （BALF） was collect- ed for determination of the total protein concentration; white blood cell （WBC） counts and concentrations of MIF, IL-6 and IL-1β （by ELISA）. Then the rats were sacrificed and the lungs removed for microscopic examination and for determination of wet to dry lung weight ratio （W/D ratio） and expression of MIF mRNA （by RT-PCR）. Results Compared with C and S groups, WBC counts, concentrations of total protein, MIF, IL-6 and IL-1β in BALF, and W/D ratio and expression of MIF mRNA in lung tissues were significantly increased in group L （P 〈 0.05）. There was no significant difference in the indexes mentioned above between group C and group S （ P 〉 0.05 ）. The pathological changes occurred in group L. Conclusion The up-regulation of MIF mRNA expression in lung tissues may be involved in the development of ventilator-induced lung injury in rats. Key words: Respiration, artificial;  Respiratory distress syndrome, adult;  Macrophage migration-in-