Objective:To investigate the effect of IRH on pulmonary fibrosis and its intervention mechanism.Methods:45 sprague-dawley rats were randomly divided into three groups.The model group and the intervention group were received endotracheal injection of bleomycln to induce pulmonary fibrosis

while the control group were received endotracheal injection of saline.From the second day the intervention group IRH were injected to the stomach

while the other two groups were injected saline instead.On the 7th day

14th day and 28th day the lungs were isolated.The expression of MMP-2 and TIMP-1 was detected by immunohistochemical method respectively.Results:There was only a very weak expression of MMP-2 and TIMP-1 in the control group

there was significantly higher level in model group compared with control group on the 7th day

14th day and 28th day.The IRH group was significantly lower than the model group with the same time points

though it was also obviously higher than the control group all over the period(P<0.01).the difference has statistical significance.Conclusion:IRH may inhibit the expression of MMP-2 and TIMP-1 in the lung tissue of rat with pulmonary fibrosis

contributed to the regulation of MMP-2 and TIMP-1 balance to some extent

could alleviate bleomycin-induced pulmonary fibrosis in rats.