17β-Estradiol administration attenuates seawater aspiration-induced acute lung injury in rats

There is very little evidence on the value of administering estrogen in cases of seawater drowning which can induce acute lung injury/acute respiratory distress syndrome (ALI/ARDS). Therefore, this study aimed to investigate whether 17β-estradiol (E2) treatment can attenuate seawater aspiration-induced ALI in rats. In the experiment, ALI was induced by endotracheal instillation of seawater (4mL/kg) and the rats were then given intraperitoneal injection of E2 (5mg/kg) 20min after seawater instillation. Finally, the changes of arterial blood gases which contained hydrogen ion concentration (pH), arterial oxygen tension (PaO(2)) and arterial carbon dioxide tension (PaCO(2)) were measured and the measurement of extravascular lung water (EVLW) was observed. The pulmonary histological changes were evaluated by hematoxylin-eosin stain. The expression of aquaporins (AQPs) 1, AQP5, and estrogen receptor-β (ERβ) was measured by western blotting and immunohistochemical methods. The results showed that compared with normal saline water, seawater aspiration induced more serious ALI in rats which was markedly alleviated by E2 treatment. Meanwhile, the ERβ in lung tissues was activated after E2 administration. The seawater aspiration group also presented with severe pulmonary edema which was paralleled with over expressed AQP1 and AQP5. However, the up-regulation of AQP1 and AQP5 was suppressed by the administration of E2, resulting in an attenuation of lung edema. In conclusion, E2 treatment could effectively attenuate seawater aspiration-induced acute lung injury in rats by the down-regulation of AQP1 and AQP5.