Ayling C M, Moreland B H, Zanelli J M, Schulster D
National Institute for Biological Standards and Control, South Mimms, Potters Bar, Hertfordshire.
J Endocrinol. 1989 Dec;123(3):429-35. doi: 10.1677/joe.0.1230429.
The studies describe alterations after hypophysectomy in the proportion of the type-1 and type-2 fibres in rat skeletal muscles, and the effects of replacement treatment with pituitary human (h) GH. Cytochemical analysis of myosin ATPase, succinate dehydrogenase and lactate dehydrogenase activities in sections of rat hind limb muscles were used as markers of fibre type and revealed that hypophysectomy reduced the proportion of type-1 fibres by 50% in soleus and in extensor digitorum longus muscles. This reduction in the proportion of type-1 fibres was accompanied by the appearance of transitional fibres (type 2C/1B). Following seven daily injections of hGH (60 mIU/day) to hypophysectomized rats, the proportion of type-1 fibres in both soleus and in extensor digitorum longus was increased with a concomitant reduction in the number of transitional fibres. After 11 days of treatment, all these transitional fibres had reverted back to type-1 fibres. Only hGH was observed to elicit this effect; injections of other pituitary hormones had no effect on the proportions of these transitional fibres. These alterations in fibre type occurred more rapidly than the changes reported after prolonged electrical stimulation of muscle or following extended exercise. These findings suggest that hypophysectomy and GH injection can result in a rapid alteration in the fibre composition of skeletal muscle, which may have important implications in terms of the resistance to fatigue and speed of contraction of the muscle.
这些研究描述了大鼠垂体切除术后骨骼肌中1型和2型纤维比例的变化，以及垂体人（h）生长激素替代治疗的效果。对大鼠后肢肌肉切片中的肌球蛋白ATP酶、琥珀酸脱氢酶和乳酸脱氢酶活性进行细胞化学分析，以此作为纤维类型的标志物，结果显示垂体切除术后比目鱼肌和趾长伸肌中1型纤维的比例降低了50%。1型纤维比例的降低伴随着过渡性纤维（2C/1B型）的出现。对垂体切除的大鼠每日注射7次hGH（60 mIU/天）后，比目鱼肌和趾长伸肌中1型纤维的比例均增加，同时过渡性纤维的数量减少。治疗11天后，所有这些过渡性纤维都恢复为1型纤维。仅观察到hGH能引发这种效应；注射其他垂体激素对这些过渡性纤维的比例没有影响。纤维类型的这些变化比长期电刺激肌肉或长期运动后报道的变化发生得更快。这些发现表明，垂体切除和注射生长激素可导致骨骼肌纤维组成的快速改变，这可能对肌肉的抗疲劳能力和收缩速度具有重要意义。
