Effects Of Exogenous Metallothionein On Antioxidation Capacity And GSH-Px, CAT Gene Expression In Dairy Cattle

To approach the effects of exogenous metalloehionein on antioxidation regulatory mechanism and GSH-Px gene expression and CAT gene expression in dairy cattle,an expriment was conducted with 24 lactaing cows,which were randomly divided into four groups A,B,C and D,and supplemented with 0,4.0,8.0 and 12.0 mg Zn-MT respectively by intravenous injection.All under the same environment conditions,the same feedstuff, nutrition level and mamagement way.The milk yields were recorded every day.The blood samples were collected every 15 days,the activities of CAT and GSH-Px were mensurated, and the levels of CAT gene expression and GSH-Px gene expression in the cows were also determined.The results showed as follows:1.Effects of exogenous metallothionein on milk yields and butterfat percentage of dairy cattleThe first day of the experiment,there were no significant differences(P＞0.05) in milk yields among different treatments.The milk yields of the cows in group B on the 15th day were greater than those group A.The milk yields of the cows in group D on the 15th day and the 30th day were higher(P＞0.05) than group A.All treatments had no significant difference on butterfat percentage during the experimental period(P＞0.05),which only showed a little increase in group B,group C and group D.On the 30th day,all increased by 2.48%,3.28%and 4.75%respectively compared with group A,and had no significant difference(P＞0.05).2.Effect of exogenous metallothionein on serum antioxidant indices of dairy cattleAt the beginning of the experiment,the activities of GSH-Px,CAT,T-AOC and the content of MDA all had no significant difference in dairy cattle in different groups (P＞0.05).On the 15th day,the activity of GSH-Px and CAT were higher in group B,group C and group D compared with group A(P＜0.05),the activity of T-AOC was higher in group C and group D compared with group A(P＜0.05),the contens of MDA in all groups were significantly lower than group A.On the 30th day,the activity of GSH-Px,CAT and T-AOC in all treatments were higer(P＜0.05 or P＜0.01) than those in the group A,the contents of MDA in group C was significantly lower than group A. 3.3.Effect of exogenous metallothionein on blood antioxidant enzyme gene expression in dairy cattleBefore supplying exogenous metallothionein,the gene expression levels of GSH-Px and CAT had no significant difference in dairy cattle among different groups(P＞0.05). During the experiment,some extends have improved in three test groups.On the 15th day,the gene expression levels of CAT in all test groups were significant higher than group A.On the 30th day,the gene expression levels of CAT in group D was significant higher than group A.Comparing with the different period of dairy cattle in the experiment, on the 15th day and on the 30th day,the gene expression levels of CAT were higer(P＜0.05) than the first day with the same group in group C and group D.The gene expression levels of GSH-Px had no significant difference in dairy cattle among different groups during the whole experimental periods.It was concluded that exogenous metallothionein can improve milk yields of dairy cattle while exert their own potent antioxidation,it can increase the activity of GSH-Px,CAT and T-AOC in serum,decrease the content of MDA,and improve the gene expression levels of GSH-Px and CAT in the blood.All of these suggested that exogenous MT should be a physiologically active substance effective to the antioxidantion and may be presented dose-dependent and metabolization effects.