Aquaporin-1 and inducible nitric oxide synthase MRNA in injured ovine lung tissue after treatment with arteriovenous CO₂ removal

Our group has developed percutaneous extracorporeal Arterio Venous CO₂ Removal (AVCO₂R) utilizing a low-resistance membrane gas exchanger. AVCO₂R may improve survival in respiratory distress syndrome (RDS) by reducing the barotrauma and volutrauma afforded by mechanical ventilation, while providing near-total CO₂ removal. Alternatively, use of this device may decrease inflammation through effects of improved CO₂ homeostasis or other mechanisms. To test this later hypothesis, we measured mRNA for two molecular markers, aquaporin-1 (AQP-1) and inducible nitric oxide synthase (iNOS), in a clinically relevant model of RDS produced by combined smoke inhalation and 40% full-thickness burn injury. Both AQP-1 and iNOS may be involved in the characteristic large increase in lung transvascular fluid flux observed after this injury. AQP-1 and iNOS mRNA were quantitated by a reverse transcriptase - polymerase chain reaction technique (RT-PCR) that utilized an internal, competitive standard engineered to adhere to the same primers as AQP-1 or iNOS. AQP-1 mRNA was 53,500 ± 15,373 at 48 h in ventilator treated animals and 20,520 ± 6,938 at 96 h after injury and 48 h of AVCO₂R in AVCO₂R treated animals (copies/μg total RNA, means ± S.E.M.) (p=0.07) while iNOS mRNA was 17,178 ± 3,095 at 48 h in ventilator treated animals and 7,853 ± 2,229 at 96 h after injury and 48 h of AVCO₂R in AVCO₂R treated animals (copies/μg total RNA, means ± S.E.M.) (p=0.008). These findings suggest that AVCO₂R device may be associated with decreasing expression of AQP-1 and iNOS, two molecules that may be important in the pathogenesis of RDS.