Valberg S J, Mickelson J R, Gallant E M, MacLeay J M, Lentz L, de la Corte F
Department of Clinical and Population Sciences, College of Veterinary Medicine, University of Minnesota, St Paul 55108, USA.
Equine Vet J Suppl. 1999 Jul(30):533-8. doi: 10.1111/j.2042-3306.1999.tb05279.x.
The purpose of this study was to determine if chronic exertional rhabdomyolysis (ER) in Quarter Horses and Thoroughbreds represents one or several distinct myopathies. Eighteen Quarter Horses and 18 Thoroughbreds with ER were selected from cases presented to the Veterinary Hospital on the basis of a history of ER, assessment of muscle histopathology, and serum CK activity before and 4 h post exercise. In addition, 2 of 3 of the following parameters were evaluated: muscle glycogen concentrations, thyroid hormones (T3, T4), fractional excretion (FE) of sodium, potassium and chloride. The CK response to training, the metabolic response to a near maximal standardised exercise test (SET), blood glucose concentrations after an i.v. glucose challenge and a skeletal muscle in vitro caffeine contracture test were performed on 5 of the Quarter Horses, selected because of polysaccharide storage myopathy (PSSM), and 5 of the Thoroughbreds. Serum T3 and T4 were all within normal limits. Low FE of sodium and potassium were seen in < 20% of Quarter Horses and Thoroughbreds. Four hours post exercise, CK was increased in 77% of Quarter Horses and 72% of Thoroughbreds with ER. Muscle glycogen concentrations in Quarter Horses with ER were significantly higher than in normal Quarter Horses and Thoroughbreds with ER. No Thoroughbreds, but 15/18 Quarter Horses with ER had abnormal polysaccharide accumulation in muscle biopsies consistent with a diagnosis of PSSM. PSSM Quarter Horses had higher CK activity during training than Thoroughbreds and higher glycogen utilisation with the SET. PSSM Quarter Horses also had significantly enhanced glucose clearance compared to normal Quarter Horses and Thoroughbreds with ER. Thoroughbreds with ER had significantly lower thresholds for caffeine-induced contracture than normal horses and PSSM Quarter Horses. It was concluded that there are multiple causes for exertional rhabdomyolysis. In Quarter Horses, rhabdomyolysis is commonly due to a glycogen storage disorder, PSSM, and is readily expressed in untrained horses. In Thoroughbreds, ER is commonly due to an underlying abnormality of muscle contraction. Rhabdomyolysis in Thoroughbreds, however, is only expressed intermittently when key stressors are present.
本研究的目的是确定夸特马和纯种马的慢性运动性横纹肌溶解症（ER）是代表一种还是几种不同的肌病。根据ER病史、肌肉组织病理学评估以及运动前和运动后4小时的血清肌酸激酶（CK）活性，从就诊于兽医医院的病例中选取了18匹夸特马和18匹纯种马患有ER。此外，对以下参数中的2/3进行了评估：肌肉糖原浓度、甲状腺激素（T3、T4）、钠、钾和氯的分数排泄（FE）。对5匹因多糖贮积性肌病（PSSM）而被选中的夸特马和5匹纯种马进行了CK对训练的反应、对接近最大标准化运动试验（SET）的代谢反应、静脉注射葡萄糖激发后的血糖浓度以及骨骼肌体外咖啡因挛缩试验。血清T3和T4均在正常范围内。在不到20%的夸特马和纯种马中观察到低钠和低钾分数排泄。运动后4小时，77%的患有ER的夸特马和72%的患有ER的纯种马CK升高。患有ER的夸特马的肌肉糖原浓度显著高于正常夸特马和患有ER的纯种马。没有纯种马，但18匹患有ER的夸特马中有15匹在肌肉活检中有异常多糖积累，符合PSSM的诊断。患有PSSM的夸特马在训练期间的CK活性高于纯种马，并且在SET中糖原利用率更高。与正常夸特马和患有ER的纯种马相比，患有PSSM的夸特马的葡萄糖清除率也显著提高。患有ER的纯种马对咖啡因诱导的挛缩阈值明显低于正常马匹和患有PSSM的夸特马。得出的结论是，运动性横纹肌溶解症有多种原因。在夸特马中，横纹肌溶解症通常是由于糖原贮积障碍，即PSSM，并且在未经训练的马匹中很容易表现出来。在纯种马中，ER通常是由于肌肉收缩的潜在异常。然而，纯种马的横纹肌溶解症仅在存在关键应激源时间歇性表现出来。
