title: Effect of N-2-mercaptopropionyl glycine on exercise-induced cardiac adaptations.
abstract: The purpose of this study was to test the hypothesis that exercise-induced cardiac adaptations would be attenuated by the free radical scavenger N-2-mercaptopropionyl glycine (MPG). Male Sprague-Dawley rats were divided into four groups (n = 9-13 per group) for 3-4 wk: sedentary (S), S+MPG (100 mg/kg ip daily), exercised on a treadmill (E) (60 min/day, 5 days/wk, at a speed of 20 m/min up a 6° grade in a 6°C room), or E+MPG given 10 min prior to exercise. Additional rats (n = 55) were used to determine acute exercise effects on myocardial redox state [nonprotein nonglutathione sulfhydryls (NPNGSH)] and PI3K/Akt signaling pathway activation. Compared with S, NPNGSH levels were 48% lower in E (P < 0.05) and unchanged in E+MPG (P > 0.05). MPG also attenuated exercise-induced activation of the signaling proteins Akt and S6. Hearts from the 4-wk groups were weighed, and cardiac function was evaluated using an isolated perfused working heart preparation. Similar increases (P < 0.05) in both exercised groups were observed for heart weight and heart weight-to-body weight ratio. Cardiac function improved in E vs. S, as indicated by greater (P < 0.05) external work performed (cardiac output × systolic pressure) and efficiency of external work (work/Vo(2)). MPG prevented these exercise-induced functional improvements. Skeletal muscle mitochondria content increased to similar levels in E and E+MPG. This study provides evidence that free radicals do not play an essential role in the development of exercise-induced cardiac hypertrophy; however, they appear to be involved in functional cardiac adaptations, which may be mediated through the PI3K/Akt pathway.
authors.affiliation: Department of Kinesiology and Health Education, University of Texas, Austin Texas, USA.
authors.forename: Matthew J
authors.initials: MJ
authors.lastname: Nelson
authors.forename: M Brennan
authors.initials: MB
authors.lastname: Harris
authors.forename: Marvin O
authors.initials: MO
authors.lastname: Boluyt
authors.forename: Hyun Seok
authors.initials: HS
authors.lastname: Hwang
authors.forename: Joseph W
authors.initials: JW
authors.lastname: Starnes
mesh_terms: D000818:Animals; D000975:Antioxidants / Q000494:pharmacology*; D005609:Free Radicals / Q000378:metabolism; D006321:Heart / Q000187:drug effects* / Q000502:physiology*; D006706:Homeostasis / Q000502:physiology; D008297:Male; D023421:Models, Animal; D010084:Oxidation-Reduction; D019869:Phosphatidylinositol 3-Kinases / Q000502:physiology; D010805:Physical Conditioning, Animal / Q000502:physiology*; D010807:Physical Endurance / Q000187:drug effects / Q000502:physiology; D051057:Proto-Oncogene Proteins c-akt / Q000502:physiology; D051381:Rats; D017207:Rats, Sprague-Dawley; D015398:Signal Transduction / Q000187:drug effects / Q000502:physiology; D008625:Tiopronin / Q000494:pharmacology*
chemical_list: D000975:Antioxidants; D005609:Free Radicals; D008625:Tiopronin; D019869:Phosphatidylinositol 3-Kinases; D051057:Proto-Oncogene Proteins c-akt