The Intervention Of Spironolactone On Pulmonary Fibrosis Induced By Paraquat Poisoning In Rats And Experimental Study Of Its Mechanisms

【Objectives】The study was to establish a pulmonary fibrosis model induced by paraquat poisioning in rat by one--hit intragastrically and aimed to obsevre whether spironolactone would ameliorate pulmonary fibrosis induced by paraquat in rats so as to investigate the dymanic menchanisms of paraquat- induced pulmonary fibrosis and explore the possible mechanisms of protective effect.【Methods】Sixty-three adult healthy male Sprague-Dawley (SD) rats were randomly divided into three groups of different treatments designated as: normal control group (control group),PQ administration group (PQ group) and paraquat +spironolactone group (PQ+SPI group). Each group was randomly divided into three subgroups of seven rats each according to 7, 14 or 28 days. The rats in PQ group and PQ+SPI group were treated intragastrically ( i.g. ) with PQ ( 80mg/kg ) while the rats in control group were treated with the same dose of saline at the beginning of the experiment. Two hours after intragastrication, spironolactone (100mg/kg) was perfused into stomach once a day respectively in the PQ+SPI group while the rats in PQ group and control group received daily saline. The rats in each group were killed at either 7, 14 or 28 days after PQ administration. At the given timepoint, blood fluids and lung tissues were harvested before the rats were sacrificed. The body weight and lung wet weight of rats were measured, and the weight gain and lung coefficient of rats in each group were measured and compared. The right lung in each group rat was excised for HE staining and Masson Staining and hydroxyproline in left lung tissues were used to determine the severity of pulmonary alveolitis and fibrosis. Radioimmunoassay(RIA) was used to determine aldosterone levels of the plasma and left lung tissue in each group. The levels of protein expression of TGF-β1 andα-SMA in lung tissue were detected by immunohistochemistry staining and the mean optical density of TGF-β1 andα-SMA were determined by semquantitative picture analysis.【Results】(1) The intoxication manifestation of PQ group was much more serious than that of control group and PQ+SPI group. The Rat body weight gain of PQ group evidently decreased while on every timepoint the scores of pulmonary alveolitis and fibrosis, lung coefficiet, hydroxyproline contents in lung tissue were more prominent in the PQ group compared to control group (P<0.01). The ALD level of plasma and lung tissue on every timepoint were significantly higher than that of control group, there was significant difference on 14d and 28d (P<0.05) after PQ administration. The mean optical density of TGF-β1 andα-SMA protein expression in lung tissue of PQ group at every timepoint was much higher than those of control group and PQ+SPI group, there was significant difference on 14d and 28d (P<0.05 or P<0.01).(2) The intoxication manifestation of PQ+SPI group was no more serious than that of PQ group. The rats of PQ+SPI group decreased in body weight gain and the PQ+SPI group at every phase has the same change leision as PQ group; but the degree of pulmonary alveolitis and fibrosis decreased than that of PQ group (P<0.05 or P<0.01). The scores of pulmonary alveolitis and fibrosis at every timepoint were lower than that of PQ group(P<0.05 or P<0.01). The pulmonary index, HYP contentrations were higher than that of control group at every phase,but lower than than that of PQ group(P<0.01). The ALD level of plasma and lung tissue in PQ+SPI group increased compared with control group and PQ group at the same timepoint, there were significant difference on 14d and 28 d (P<0.05). The mean optical density of TGF-β1 protein expression in lung tissue of PQ+SPI group was higher than that of control group,but significantly lower than that of PQ group at every timepoint, there was significant difference on 14d and 28d (P<0.05 or P<0.01). The mean optical density ofα-SMA protein expression in lung tissue were not markedly decreased compared with PQ group and control group on 7d (P>0.05), but there were significant difference between the two groups on 14d and 28d (P<0.01). 【Conclusions】The rat model of paraquat-induced pulmonary fibrosis can be successfully reproduced by one--hit paraquat(80mg/kg) intragastrically, which fitted with the avene of the clinical PQ poisioning. The conclusion was drawed that ALD, TGF-β1 andα-SMA may all play an important role in particating in the formation and development of pulmonary fibrosis following paraquat- induced lung injury in rats. Spironolactone may have a protective effect on paraquat-induced pulmonary fibrosis in rats, and the effect may be due to inhibition of aldosterone receptor and, in part, be associated with reduction in the protein expression of TGF-β1 andα-SMA.