Suwannachot P, Verkleij C B, Kocsis S, Enzerink E, Everts M E
Department of Anatomy and Physiology, Faculty of Veterinary Medicine, Utrecht University, PO Box 80.157, 3508 TD Utrecht, The Netherlands.
J Endocrinol. 2000 Nov;167(2):321-9. doi: 10.1677/joe.0.1670321.
We determined the effects of food supply and low-intensity training on growth, serum thyroid hormone levels and the Na(+),K(+)-pump concentration in equine skeletal muscle. Twenty-two Shetland ponies were subjected to two different feeding regimes for 2(1/2) years (11 ponies per group): food restriction (body condition score kept at 2) or ad libitum fed (body condition score kept at 8). Five ponies in each group underwent low-intensity training. Gluteus medius muscle and serum samples were obtained in April 1998. Subsequently, all ponies were fed ad libitum and the training programme was stopped. Muscle biopsies and serum samples were collected again in November 1998. Food restriction was associated with a 30-50% reduction of body weight gain. While the total thyroxine (T(4)) level was increased, the free T(4) remained at the control level. The serum total tri-iodothyronine (T(3)) and free T(3) were reduced by 30% and 49% respectively. After 6 months of refeeding there were no differences in any of the hormone levels between the ad libitum fed and the food-restricted groups. Food restriction produced a minor, but not significant, decrease in the Na(+),K(+)-pump concentration in the gluteus medius muscle of the Shetland ponies. Low-intensity training reduced weight gain of the ad libitum fed group by 25%, but had no detectable effect on the concentration of the Na(+), K(+)-pumps. We conclude that prolonged food restriction in Shetland ponies results in a weight gain reduction of 30-50%, and is associated with similar decreases in serum total and free T(3). The reduction in serum T(3) only slightly influenced the Na(+), K(+)-ATPase concentration in skeletal muscle, indicating that muscle tissue of different species may respond differently to changes in circulating thyroid hormones.
我们测定了食物供应和低强度训练对马骨骼肌生长、血清甲状腺激素水平以及钠钾泵浓度的影响。22匹设得兰矮种马被分为两组，分别采用两种不同的饲养方式，持续2年半（每组11匹）：食物限制组（体况评分维持在2分）或自由采食组（体况评分维持在8分）。每组中有5匹马进行低强度训练。1998年4月采集臀中肌肌肉和血清样本。随后，所有马匹改为自由采食，训练计划停止。1998年11月再次采集肌肉活检样本和血清样本。食物限制导致体重增加减少30%至50%。虽然总甲状腺素（T4）水平升高，但游离T4仍维持在对照水平。血清总三碘甲状腺原氨酸（T3）和游离T3分别降低了30%和49%。重新喂食6个月后，自由采食组和食物限制组的任何激素水平均无差异。食物限制使设得兰矮种马臀中肌的钠钾泵浓度略有降低，但不显著。低强度训练使自由采食组的体重增加减少了25%，但对钠钾泵的浓度没有可检测到的影响。我们得出结论，设得兰矮种马长期食物限制导致体重增加减少30%至50%，并伴有血清总T3和游离T3的类似降低。血清T3的降低仅对骨骼肌中的钠钾ATP酶浓度有轻微影响，表明不同物种的肌肉组织对循环甲状腺激素变化的反应可能不同。
