OBJECTIVETo investigate the protective effect of exogenous inhibitor of matrix metalloproteinases-9 (MMP-9), batimastat, in the lung injury induced by cardiopulmonary bypass (CPB) in dogs.

METHODSThirty healthy mongrel puppies were randomly divided into 3 groups: control group, low-dose group [batimastat 10 mg/(kg.d) for 3 days before operation] and high-dose group [batimastat 30 mg/(kg.d) for 3 days before operation]. The off-pump puppies' model of acute lung injury was established, and hemodynamic and respiratory parameters were monitored. The preoperative and postoperative alveolar-arterial oxygen difference (A-aDO(2)) and respiratory index (RI) were calculated. From the beginning of surgery, blood samples were taken at the time 0, 60, 120, and 270 min. Plasma concentrations of MMP-9 were measured by ELISA, and blood MMP-9 mRNA expressions were determined by RT-PCR. The myeloperoxidase (MPO) activity of centrifugal bronchoalveolar lavage fluid were measured by Colorimetry. And MMP-9 activity was determined by Gelatin zymography. Light and electronic microscope were used to observe the morphological changes of lung tissue. A small piece of left lung tissue was taken, weighed and baked to calculate the wet weight (W/D) index.

RESULTSAfter cardiopulmonary bypass, the concentrations of MMP-9 and mRNA expressions of the control group were increased significantly, and lung injury was apparent. At 270 min, the MMP-9 plasma concentration of high-dose group (17.36 +/- 1.18) microg/L was significant reducing than control group (30.47 +/- 2.22) microg/L (P < 0.05). After operation, A-aDO(2) and RI of high-dose group were significantly improved than control group (P < 0.05). The W/D index of the high-dose group (2.8 +/- 0.48) was significantly lower than that of control group (4.7 +/- 0.6) (P < 0.05). And the pathological changes of lung tissue were significantly improved in the high-dose group. However, there was no significant difference in the MMP-9 mRNA expression in three groups.

CONCLUSIONSBatimastat plays a role in the protection of the lung injury of CBP by reducing the concentration and activity of MMP-9, the degradation of the cell membrane and pulmonary neutrophil infiltration and reduction of pulmonary edema.