| Microsomal glutathione S-transferase (mGST) is one of the important detoxicity enzymes in vivo,its modifying activation by drug and the biological significance have been paid more attention to in pertinent field recently. To explore the influence of drug on mGST and its possible mechanism in vivo,and to further reveal the biological nature of these changes in enzymatic characteristic by drug and poison,we select Acetaminophen (AAP) and Cyclophoshamide (CP) that can modify activation of mGST in vitro to use in the experiment.1. Influence of AAP and CP on mGST and related enzyme activity in miceCYP2E1 was induced with 10% ethanol drinking freely and CYP was induced with 75 mg kg" phenobarbital ip in mice,respectively. GST activity in Serum,Liver cytosol and microsome of mice was measured to investigate the effect of mGST activation by drug. The results showed that:(1) On time course and dose-dependent effect of drug,AAP 90-210 mg kg-1,CP 100-200 mg kg-1 increased the activities of sALT,sGST,mGST and decreased cGST activity dramaticcally in mice. All these were dose dependent ( P <0.05-0.01). AAP CP 150 mg kg-1 increased sALT,sGST,mGST activities and decreased cGST activity,markedly at 2,3 hr respectively ( P <0.01- 0.001). (2) Relativity analysis of mGST and sGST,cGST activities of AAP,CP treated mice showed agood positive correlation between mGST and sGST activity (r=0.9750,r=0.9909,respectively) and a negative correlation between mGST and cGST activity (r=-0.9700,-0.9676,respectively) on dose relation at 2,3 hr,respectively. These suggest that the liver toxicity of drug cause the variety of mGST and other related enzyme activity.2. Study on regulation path and way of mGST activity2.1 Effect of AAP and CP on MDA and GSH content in liver of miceTo explore the influence possible mechanism of drug on mGST activity,MDA and GSH content were measured after drug ip treatment to explain whether drug and its metabolites caused liver lipid peroxidation and the variety of GSH content of mGST substrate or not. The results showed that:(1) On time course and dose-dependent effect of drug,AAP 90-210 mg kg-1,CP 100-200 mg kg-1 increased MDA content declined GSH content first and increased it later in liver,All these were dose dependent. AAP 100-200 mg kg"'> CP100-200 mg kg"1 increased MDA content in liver homogenate,markedly at 6 hr. It also decreased GSH content,markedly at 1 hr,increased sharply at 3-6 hr,markedly at 6 hr( P <0.05- 0.001). (2) Relativity analysis of mGST activity and MDA,GSH content showed:a good positive correlation between mGST activity and MDA content(r=0.9334,r=0.9330,respectively) and a negative correlation between mGST and(r=-0.9450,-0.9221,respectively) on dose relation at 2,3 hr respectively.These suggests that MDA content increasing,GSH being exhausted is the result of the liver lipid peroxidation by drug and oxidative stress is involved in the way of mGST activation.2.2 Effect of AAP and CP on GSH-Px activity in the cytosol and microsome of micecGSH-Px and mGSH-Px activity were measured after drug ip treatment to observe the variey of mGST,which functions as mGSH-Px,and related mGSH-Px activity. The results showed that:(1) On time course and dose-dependent effect of drug,AAP 90-210 mg kg-1,CP 100-200 mg kg-1 increased mGSH-Px activity in the cytosol,cGSH-Px activity declined first and increased later. All these were dose dependent. AAP 100-200 mg kg-1 CP 100-200 mg kg-1 increased mGSH-Px,declined cGSH-Px activity,markedly at 2,3 hr,respectively (P<0.01- 0.001). (2) Relativity analysis of mGST and GSH-Px activity showed:a good positive correlation between mGST and mGSH-Px activity (r=0.9875,r=0.9990,respectively) and a negative correlation between mGST and cGSH-Px activity (r=-0.9823,-0.9221,respectively)on dose relation at 2,3 hr respectively. These suggest that oxidative stress by drug cause activation of mGST and mGSH-Px at same time.2.3 Kinetic parameters of mGST and mGSH-Px of AAP or CP treated miceTo study the variety of mGST and related...
|
PDF Full Text Request