title: Creatine supplementation affects sprint endurance in juvenile rainbow trout.
abstract: Fingerling rainbow trout were supplemented with equal amounts of creatine (Cr) by two routes: dietary (12.5 mg Cr per g food); or intraperitoneal injection (0.5 mg Cr per g fish). Endurance in a fixed velocity sprint test (at a speed of 7 BL s(-1)), and resting levels of white muscle metabolites (total creatine [a measure of free creatine plus phosphocreatine (PCr), ATP, lactate and glycogen] were assessed following 7 days of supplementation and compared to controls. None of the treatments had a significant effect on growth, muscle total creatine, percent phosphorylation of creatine, ATP or lactate. However, resting muscle glycogen was elevated in creatine-supplemented fish. Higher muscle glycogen corresponded to significantly greater endurance in creatine-supplemented fish. Although fish do not actively transport additional creatine into the muscle, a mechanism whereby circulating creatine acts to enhance muscle glycogen is present. These results suggest that the improved endurance may be due to an insulin-dependent mechanism (similar to that elucidated in mammalian studies) that allows fish to supercompensate muscle glycogen stores, thus extending endurance through enhanced glycolytic flux.
authors.affiliation: Department of Biology, McMaster University, Hamilton, Ontario, Canada. wmcfarla@sciborg.uwaterloo.ca
authors.forename: W J
authors.initials: WJ
authors.lastname: McFarlane
authors.forename: G J
authors.initials: GJ
authors.lastname: Heigenhauser
authors.forename: D G
authors.initials: DG
authors.lastname: McDonald
mesh_terms: D000255:Adenosine Triphosphate / Q000378:metabolism; D000824:Animal Nutritional Physiological Phenomena; D000818:Animals; D003401:Creatine / Q000008:administration & dosage / Q000096:biosynthesis / Q000494:pharmacology*; D019587:Dietary Supplements; D004305:Dose-Response Relationship, Drug; D006003:Glycogen / Q000096:biosynthesis / Q000378:metabolism; D007328:Insulin / Q000378:metabolism; D019344:Lactic Acid / Q000378:metabolism; D009132:Muscles / Q000378:metabolism; D017686:Oncorhynchus mykiss; D010766:Phosphorylation; D010805:Physical Conditioning, Animal; D010809:Physical Fitness
chemical_list: D007328:Insulin; D019344:Lactic Acid; D000255:Adenosine Triphosphate; D006003:Glycogen; D003401:Creatine