The Inchoate Alteration Of Pulmonary Surfactant In Oleic Acid-induced Acute Lung Injury In Rats And The Protective Effect Of β-adrenergic Receptor Agonists In Vivo

ObjectiveThe purpose of this experiment was to study the method of reproducing themodel of acute lung injury (ALI) in rats through Oleic Acid (OA) vein injection, andinvestigate the alteration in pulmonary surfactant (PS) after ALI induced by OA, andexplore the protective effect and the mechanism of beta-adrenergic receptoragonists-Isoprenaline hydrochloride in OA induced ALI in rats, so providing a newclinical method in treating ALI.MethodsOA (0.12ml/kg) was used to reproduce the model of ALI in rats. Seventy-eightadult Sprague-Dawley rats were randomly divided into three groups which were ALIinduced by oleic acid injection (OA group, n=30), therapy group treated byIsoprenaline hydrochloride injection (I&O group, n=30) and normal control treated bysaline injection (NS group, n=18). Arterial oxygen tension (PaO₂), arterial carbondioxide tension (PaCO₂), power of hydrogen (pH) and serum surfactant associatedprotein A (SP-A) level were assayed after the animals were exsanguinated andsacrificed at 1, 2 and 4 hours. The left lung was used for measurements of wet / dryweight ratio(W/D) ,histopathology and beta-adrenergic receptor(β-AR), whereasthe right lung was lavaged and determined the total proteins(TP), totalphospholipids(TPL), phosphatidylcholine (PC) and SP-A in the bronchoalveolarlavage fluid(BALF).ResultsTPL, PC/TPL and SP-A of OA group in the BALF were significantly andprogressively decreased (P<0.01) from 1 hour after oleic acid injection whereas, TPW/D and serum SP-A concentration were progressively increased (P<0.05) ascompared with NS group. What's more, β-AR in pulmonary tissue weresignificantly decreased (P<0.01), and the values of SP-A in the BALF were negativelycorrelated to those in the serum in OA group at same time points(rOA1= -0.914,P<0.05;rOA2= -0.923,P<0.01;rOA4= -0.910,P<0.05). There were obvious pathologicalmanifestations of ALI. TPL, PC/TPL and SP-A of I&O group in the BALF weresignificantly increased (P<0.05) whereas TP W/D, and serum SP-A were significantlydecreased (P<0.05) as compared with OA group at same time points. Compared withthe OA group at same time points, the pathological manifestations of rat's lung wereameliorated and theβ-AR in pulmonary tissue were nonsignificant(P>0.05).Conclusions The method of reproducing the model of ALI in rats through OA vein injectionwas good. The PS inactivation may be the important internal causes during the earlycourse of ALI induced by oleic acid injection. The serum SP-A concentration in ALIrats was significantly elevated, so serum SP-A was a lung-specific serum marker forthe diagnosis of ALI. β-adrenergic receptor agonists may lesson the development ofALI induced by oleic acid injection to some extent.