C-15L Free Communication/Poster Cellular/Molecular Physiology of Muscle
We reported that the peroxisome proliferator-activated receptor γ coactivator-1 (PGC-1) mRNA in rat epitrochlearis (EPI) muscle was significantly increased after 18-h incubation with AICAR (a AMPK activator)(BBRC,2002). Since AMPK was shown to be activated in an exercise-intensity dependent manner, in the present investigation, we assessed the effects of short-lasting high-intensity swimming exercise, which is postulated to substantially increase AMPK activity, on PGC-1 protein content in rat EPI muscle, and to compare its effects on PGC-1 protein with that observed after low-intensity prolonged swimming exercise, which is known to increase PGC-1 mRNA.
Male SD rats (5–6 week-old) were randomly assigned to high-intensity swimming exercise (HIS), or low intensity swimming exercise (LIS). Age-matched sedentary rats were used as a control (CON). During HIS, the rats repeated fourteen 20-s swimming with a weight equivalent to 14% of body weight. Between exercise sessions, a 10-s pause was allowed. Rats in the LIS group swam without a load for 6-h in two 3-h sessions, separated by 45-min rest.
PGC-1 protein in rat EPI muscle was significantly increased by 126, 140, and 126% at 2-h, 6-h, and 18-h, respectively, after HIS, compared with that of the CON muscle (p < 0.001). Immediately, 6-h, and 18-h after the LIS, the PGC-1 protein content in the muscle was significantly elevated by 84, 95, and 67%, respectively (p < 0.001). The increment in PGC-1 protein at 6-h after the HIS did not differ from that observed after the LIS at the same time point. Both HIS and LIS induced significant increases (7- and 3-fold higher than that of CON muscle, respectively) in AMPK activity.
The present investigation demonstrated that the PGC-1 protein in rat EPI muscle rapidly increased in response to an acute bouts of swimming exercise. Further, the results showed that extremely high-intensity intermittent swimming exercise lasting only 280 s elevated the PGC-1 protein in rat EPI muscle to a level comparable to that attained after the 6-h low-intensity swimming exercise.