Effect of mechanical ventilation on urine volume and expression of aquaporins in rabbits

摘要

Objective:To explore biological mechanisms underlying the traditional Chinese medicine theory of 'lung governing the regulation of water passage' by observing effects of mechanical ventilation on urine volume and related bioactive substances.Methods:A total of 16 male rabbits were randomly divided into control and lung expansion model groups (n =8 per group),which were examined during the following four respiratory intervention stages (10 minutes each):(1) free breathing without any respiratory intervention;(2) lung expansion induced by mechanical ventilator;(3) free breathing without ventilator intervention;(4) cutting of bilateral sympathetic,vagus,and depressor nerves with mechanical ventilation.Data for breathing rate,blood pressure,and urine drops were recorded with a Medlab data acquisition system.Levels of nitric oxide (NO),antidiuretic hormone (ADH),endothelin 1 (ET-1),angiotensin Ⅱ (AngⅡ),prostaglandin E2 (PGE2),and atrial natriuretic peptide (ANP) were detected in lung tissue,kidney tissue,and serum by enzyme-linked immunosorbent assay.Protein expression of aquaporins 1 and 2 (AQP1 and AQP2) was detected in kidney tissue by immunohistochemistry,while Aqp1 mRNA and Aqp2 mRNA levels in kidney tissue were detected by real-time quantitative polymerase chain reaction.Histopathological changes in lung and kidney tissues were examined by hematoxylin and eosin staining.Results:Compared with the control group,number of urine drops during the second and fourth stages is significantly decreased in the model group (P <.05).In addition,NO and PGE2 content in lung and kidney tissues was significantly decreased in the model group (P <.05).ANP content in model group lung and kidney tissues was significantly increased (P <.05),while ET-1 content in these tissues was significantly decreased (P <.05).AngⅡ content in kidney tissue was significantly decreased in the model group (P <.05),while serum AngⅡ content of the animals was significantly increased (P <.05).Expression of AQP1 and AQP2 proteins in kidney tissue was significantly higher in the model group than in the control group (P <.05).No obvious histopathological changes were observed in lung or kidney tissues of animals in either group.Conclusions:Mechanical ventilation reduced urine volume,increased expression of AQP1 and AQP2 in kidney tissue,and altered levels of NO,ADH,ET-1,AngⅡ,PGE2,and ANP in lung tissue,kidney tissue,and serum.These results provide an experimental basis for preliminary studies of mechanisms under pinning the theory of 'lung governing the regulation of water passage'.