Methylene blue protects against oleic acid‐induced acute lung injury in rats (718.2)

Abstract

We aimed to evaluate the methylene blue (MB) effects in the lung tissue, with emphasis on capillary permeability, inhibiting the soluble guanylate cyclase (sGC) in oleic acid‐induced (OA) acute lung injury (ALI). Male Wistar rats under spontaneous breathing received 1) OA (100 or 200 mg/kg); 2) Pretreated group received MB 5 min before the OA infusion, and; 3) Treatment group received MB 2 hours after OA infusion. The MB was administered as an i.v. bolus followed by 2h of continuous infusion (3mg/kg/h). After 4 h, blood was collected for gasometry; bronchoalveolar lavage for total protein dosage and lung tissue for wet weight/dry weight (W/D) analysis, histology and amount of tissue nitric oxide (NO). ALI was characterized by the OA of 200mg/kg, the increased bronchoalveolar lavage protein and the relation W/D. The main results were: 1) It was not observed severe hypoxemia after 4 hours of ALI; 2) The pre‐treatment group showed a significant difference with lower protein quantification in bronchoalveolar lavage; 3) Although not statistically significant it was observed lower values of the W/D ratio and NO tissue in the MB groups; 4) Gross examination of the lungs revealed more severe injury in the untreated group, confirmed by histological examination whose main findings include increased infiltration of lymphocytes, alveolar membrane thickening and increased alveolar edema. These data suggest that the lung permeability decreases when MB is administered at an early stage OA‐induced ALI.Grant Funding Source: Supported by CNPq