Imaging Study About Distribution Sites Of Lesion Areas Of Pulmonary Fibrosis Induced By Paraquat

ObjectiveIt is well known that PQ is not only an effective and widely used organicheterocyclic herbicide but also a lethal poison. In many developing countriesparaquat is widely available and inexpensive, making poisoning preventiondifficult. And most of people who drink the solution of PQ as a means ofcommiting suicide due to some special causes are more likely to be poisoned.The mortality rate of the patients with PQ poisoning is very high owing to thedeficiency of effective therapeutic methods at present. Multiple organ damageswill be brought about at early phase of PQ poisoning; Also the lung as the mainPQ target organ will be developed irreversible pulmonary fibrosis with theextending of poisoning time, and respiratory failure induced by pulmonaryfibrosis could lead to the death of the poisoning patients. Now plenty ofexperiments on pathogenesis and therapies of pulmonary fibrosis induced by PQare still proceeding, but there are no explicit advances. And there is no report tomention the distribution of the lesion areas of pulmonary fibrosis up to now. Ourteam tried to look for the new breakthrough on pulmonary fibrosis from anotherangle and observe the general distribution sites of lesion areas in pulmonaryfibrosis induced by PQ. We used MicroCT system to scan the poisoning rats in vivo and detect the occurences and dynamic developments of pulmonaryfibrosis. And we made qualitative analysis to the developments via imageologymanifestations, and assessed the density of pathological tissues by means of CTvalue transformations to judge quantitatively the main lesion areas and severityof pulmonary fibrosis.MethodMethodsMethod one: 48 male SD rats were randomly assigned to control (24 ) andparaquat treatment(24 ) groups. In exposure group, the rats were consecutivelygiven dilute solution of paraquat (4 mg/ml ) intraperitoneal injection at 14mg/kg at once and the control group were treated with the same volume ofsaline. 4 rats were taken out from every group to scan lung tissues in vivo byMicro CT system on day 3, 7, 14, 28 respectively after administration and otherswere executed respectively on the four days mentioned above. General situationof the lung, pulmonary index, histological examination and hydroxyprolinecontent were used to determine the severity of pulmonary fibrosis.Method two: 15 male SD rats were randomly assigned to control (5 ) andparaquat poisoned (10 ) groups .The rats in exposure and control group weretreated with dilute solution of paraquat according to method one. All rats werescanned their lung tissues in vivo by Micro CT on day 3, 7, 14, 28 respectively.In line with the data from analyses of scanned images, we compared the displayrates of the signs of fibrosis and average CT value transformations in regionsgiven(region of interest ROI ) by using statistical methods as one factor analysisof variance (t-test) or comparison among groups.ResultsResult one: Compared with the rats in control group, the rats with acuteparaquat poisoning all appeared abnormal behaviors and symptoms. We also found the signs of pulmonary alveolitis and fibrosis occurred in succession bynaked eye, optical microscope and Micro CT system with the extention ofexposure time. Pulmonary indexes of rats in exposure group were all higherthan those in control group (P＜0.05 or P＜0.01). And in poisoned group, withthe extention of exposure time, the pulmonary indexes were upregulatedsignificantly (P＜0.01). The contents of hydroxyproline of rat's lung tissues inexposure group were remarkably higher than corresponding control group onday 7, 14, 28 (P＜0.01), and in poisoned group the pulmonary indexes werealso upregulated significantly with the extention of exposure time (P＜0.01).ResulResult two: Compared with the rats of control group, the rats with acuteparaquat poisoning all appeared varying degrees of the signs of pulmonaryfibrosis, Most of the signs mainly appeared after one week of poisoning timeand predominantly spread over the exterior regions of the lower-middle side oflung. The results of average CT value transformations of ROI showed thedensity of lung was significantly upregulated with the extention of exposuretime, and also indicated there was no difference between right lung and left lungon the process of pulmonary fibrosis(P＞0.05),but there had some differenceson the distributions of fibrosis at different sites in one lung(P＜0.05 or P＜0.01).ConclusionsMicroCT system can be used for detection of pulmonary fibrosis in rats.The signs of pulmonary fibrosis induced by paraquat predominantly appearedafter one week of poisoning time. The density of lung is gradually increaseingwith the process of pulmonary fibrosis in rats in paraquat poisoned group, andlesion areas predominantly spread over the exterior regions of the lower-middleside of lung.