Assessment of alterations in triglyceride and glycogen concentrations in muscle tissue of Alaskan sled dogs during repetitive prolonged exercise.
OBJECTIVE
To assess changes in muscle glycogen (MG) and triglyceride (MT) concentrations in aerobically conditioned sled dogs during prolonged exercise.


METHODS
54 Alaskan sled dogs fed a high-fat diet.


METHODS
48 dogs ran 140-km distances on 4 consecutive days (cumulative distance, up to 560 km); 6 dogs remained as nonexercising control animals. Muscle biopsies were performed immediately after running 140, 420, or 560 km (6 dogs each) and subsequently after feeding and 7 hours of rest. Single muscle biopsies were performed during recovery at 28 hours in 7 dogs that completed 560 km and at 50 and 98 hours in 7 and 6 dogs that completed 510 km, respectively. Tissue samples were analyzed for MG and MT concentrations.


RESULTS
In control dogs, mean +/- SD MG and MT concentrations were 375 +/- 37 mmol/kg of dry weight (kgDW) and 25.9 +/- 10.3 mmol/kgDW, respectively. Compared with control values, MG concentration was lower after dogs completed 140 and 420 km (137 +/- 36 mmol/kgDW and 203 +/- 30 mmol/kgDW, respectively); MT concentration was lower after dogs completed 140, 420, and 560 km (7.4 +/- 5.4 mmol/kgDW; 9.6 +/- 6.9 mmol/kgDW, and 6.3 +/- 4.9 mmol/kgDW, respectively). Depletion rates during the first run exceeded rates during the final run. Replenishment rates during recovery periods were not different, regardless of distance; only MG concentration at 50 hours was significantly greater than the control value.


CONCLUSIONS
Concentration of MG progressively increased in sled dogs undergoing prolonged exercise as a result of attenuated depletion.
McKenzie
Erica C
EC
Department of Physiological Sciences, College of Veterinary Medicine, Oklahoma State University, Stillwater, OK 74078, USA.
Hinchcliff
Kenneth W
KW
Valberg
Stephanie J
SJ
Williamson
Katherine K
KK
Payton
Mark E
ME
Davis
Michael S
MS
D000818:Animals; D004285:Dogs; D006003:Glycogen / Q000378:metabolism*; D007700:Kinetics; D018482:Muscle, Skeletal / Q000378:metabolism*; D010805:Physical Conditioning, Animal; D005082:Physical Exertion / Q000502:physiology*; D012420:Running / Q000502:physiology; D014280:Triglycerides / Q000378:metabolism*
D014280:Triglycerides; D006003:Glycogen