title: Decreased erythrocyte potassium concentration associated with exercise-related myopathy in horses.
abstract: To investigate the possibility that a disorder of potassium balance may have a role in the development of equine rhabdomyolysis, the potassium concentration within erythrocytes (RBC [K+]) and plasma (P [K+]) was measured in 3 groups of horses: group 1, eight 2-year-old fillies that had postexercise muscle soreness within 48 hours of sample collection; group 2, ten 2-year-old fillies subjected to identical management and training conditions (as fillies of group 1) and that did not have signs of myopathy; and group 3, 32 yearlings of both sexes on the farm of origin of groups 1 and 2 that were pastured and not in training. Creatine kinase activity in serum from horses of groups 1 and 2 was also measured. The mean P [K+] was not significantly different between groups, whereas the mean RBC [K+] was significantly (P less than 0.01) lower in group-1 fillies vs group-2 fillies and group-3 horses. Group-1 fillies also had markedly high serum creatine kinase activity. Results of the study revealed significantly lower RBC [K+] in horses that had had signs of myopathy within the preceding 48 hours. This does not prove a causal relationship between RBC potassium depletion and myopathy, but does suggest that decreased RBC [K+] may be observed in horses with exercise-related myopathy.
authors.affiliation: Peterson & Smith Equine Hospital, Ocala, FL 32674.
authors.forename: F T
authors.initials: FT
authors.lastname: Bain
authors.forename: A M
authors.initials: AM
authors.lastname: Merritt
mesh_terms: D000818:Animals; D004912:Erythrocytes / Q000032:analysis*; D005260:Female; D006734:Horse Diseases / Q000097:blood* / Q000209:etiology; D006736:Horses; D008297:Male; D009135:Muscular Diseases / Q000097:blood / Q000662:veterinary*; D010805:Physical Conditioning, Animal; D011188:Potassium / Q000097:blood*; D012206:Rhabdomyolysis / Q000209:etiology / Q000662:veterinary
chemical_list: D011188:Potassium