Expression of Smad Gene and Protein in the Development of Exercise-induced Atrial Damage and Fibrosis

Objectives:This study was carried out to determine the expression of smad gene and protein in the development of exercise-induced atrial fibrosis.Methods:48adult male spraguedawley rats,8-week old,were randomly divided into two groups:Control group(C),and Highly intensive exercise group(H).Then each group is divided into 8 weeks,12 weeks and 16 weeks group.Group H were trained for 8weeks,12 weeks and 16 weeks of treadmill exercise respectively.mRNA and protein expression of Smad-2,Smad-4and Smad-7 were detected by Real time PCR and Western Blot.Results:Smad-2expression of H group has a trend of increase,but there was no significant difference,compared to control group.mRNA and protein expression of Smad-4increased significantly after 16week-highly-intensive exercise(P<0.05,P<0.01).Smad-4 mRNA expression increased with the extension of time,thus the Smad-4mRNA expression of H group after 16 weeks is significantly higher than 8weeks(P<0.05).Aftre 16week-highly-intensive exercise,mRNA and protein expression of Smad-7significantly decreased(P<0.05).Smad-7 mRNA and protein expression gradually reduced after 12and16 weeks of highly intensive exercise(P<0.05).With the extension of time,Smad-7 mRNA expression reduced gradually.Thus the Smad-4 mRNA expression of H group after 16 weeks is significantly lower than 8 weeks(P<0.01).Conclusion:Long-term highly intensive exercise caused the expression of atrial Smad-4increase,while progressive decrease of the Smad-7,inducing disorders between Smad,Which may be the molecular pathological mechanism of exercise-induced atrial fibrosis.