Expression of aquaporin 5 in lung tissue in a rat model of ventilator-induced lung injury

Objective To investigate the expression of aquaporin 5(AQP5)in lung tissue in a rat model of ventilator-induced lung injury(VILI).Methods Seventy pathogen free male SD rats were anesthetized with intraperitoneal 10% chloral hydrate 3.5 ml/kg,trachcostomized and mechanically ventilated.The animals were randomly assigned into 7 groups(n = 10 each)according to the tidal volume(V_T),respiratory rate(RR)and duration of mechanical ventilation: group A spontaneous breathing; group B_1,B_2(V_T 7 ml/kg,RR 50 bpm,I:E1 : 3,duration 2 h,4 h); group C_1,C_2(V_T 20 ml/kg,RR 50 bpm,I: E 1 : 3,duration 2 h,4 h)and group D_1,D_2(V_T 40 ml/kg,RR 50 bpm,I: E 1 : 3,duration 2 h,4 h).The animals were killed at the end of mechanical ventilation.The lungs were removed for microscopic examination,and determination of wet to dry lung weight ratio(W/D ratio),PMN counts in broncho-alveolar lung lavage fluid(BALF)and expression of AQP5 mRNA and protein in lung tissue.Results The expression of AQP5 mRNA and protein was significantly down-regulated while W/D ratio and PMN counts in BALF were significantly increased in group C and D than in group A and B.Conclusion The down-regulation of AQP5 expression in lung tissue may be involved in the development of lung edema during mechanical ventilation. Key words: Pneumonia,ventilator-associated;  Aquaporin 5;  Lung