| Objective: Paraquat (PQ), has been widely used as a general herbicide throughout the world. As is widely used on agricultural land within China, PQ poisoning is also gradually increasing. Although PQ is very effective as a herbicide, it is highly toxic to humans and animals. But the poisoning mechanism has not been fully elucidated, and there is lack of antidote heretofore. So PQ-induced changes of pathophysiology are becoming a hotspot in toxic therapeutics. To study the mechanism of PQ-induced lung fibrosis and the effect of Salvia miltiorrhiza monomer IH764-3 on it, structure, ultrastructure and the gene expression changes of matrix metalloproteinase 2 (MMP-2) and membrane-type 1 metalloproteinase (MT1-MMP) were studied in lung of PQ-poisoned rat. Methods: Ninety adult healthy Sprague-Dawley (SD) rats (45 female, 45 male) were divided into three groups at random-the control group (group A) , 6 rats, the poisoned group (group B) , 42 rats and the Salvia miltiorrhiza monomer IH764-3 treated group (group C) ,42 rats. The rats in group B and C were treated intragastrically with 1ml of PQ (50mg/kg) diluted with normal saline. The rats in group A were treated intragastrically with the same dose of normal saline as that of group B and C. The rats in group C were given 1 ml of Salvia miltiorrhiza monomer IH764-3 intraperitoneally at a dose of 40mg/kg diluted with normal saline once a day immediately after the administration of the PQ. The rats in group A and B were treated intraperitoneally with the same dose of normal saline once a day as those in group C. Six rats respectively from each of group B and C were anesthetized with ketamine at a period of 1, 3, 7, 14, 28 and 35 days after paraquat treatment. Rats were dissected, and heart lobar of right lung was quickly removed (about 100mg). It was immediately put into 4 ℃1 ‰Diethylpyrocarbonate (DEPC). After washing away the blood, it was put into 1.5ml Ependorf tube (EP tube), frozen in liquid nitrogen, and then maintained at -85℃until the RNA extraction was performed. The mRNA expression of MMP-2 and MT1-MMP were evaluated by RT-PCR quantitative analysis. Part of the left lung was stained with hematoxylin-eosin to observe its pathology, and the other part of left lung was stained to observe the ultrastructure by using electron microscope. So it is with group A. Results: 1) Clinical signs and appearances after PQ-poisoning: In group B and C all of the rats began to demonstrate the changes to different extent in their clinical signs in 30mins~2hrs, and were especially severe on day 1~day 3, including the respiratory system, psychological system, neural system and digestive system, etc. However, in group C all therats demonstrated slighter clinical changes than those in group B (especially in the respiratory system). 2) Group B demonstrated a loss of body weight on day 3 compared with that of unpoisoned, t=10.362, P<0.05. Group C did not demonstrate a loss of body weight on day 3 compared with that of unpoisoned. Body weight began to increase obviously on day 21 in group B, compared with that of unpoisoned, t=48.294, P<0.01, and compared with that of day 3, t=58.656, P<0.01. Body weight began to increase obviously on day 21 in group C, compared with that of unpoisoned, t=64.280, P<0.01, and compared with that of day 3, t=66.256, P<0.01. 3) MMP-2 mRNA: Group B: The MMP-2 gene expression increased 2.14 times higher than group A on day 1, t=0.349, P<0.01. After reaching its peak, it decreased slowly afterwards. It increased respectively 2.04, 2.09, 1.75 and 1.81 times higher than group A on day 3, 7, 14 and 21, t critical value is respectively 0.318, 0.333, 0.228 and 0.248, P<0.01. It showed no difference with group A on day 28 and 35. Group C: The MMP-2 gene expression increased 1.71 times higher than group A on day 1, t=0.218, P<0.01. It increased respectively 1.86 and 1.69 times higher than group A on day 3 and 7, t critical value is respectively 0.262 and 0.210, P<0.01. It showed no difference with group A in the other subgroups. After reaching its peak on day 3, it...
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