Gustafsson J A, Saartok T, Dahlberg E, Snochowski M, Häggmark T, Eriksson E
Prog Clin Biol Res. 1984;142:261-90.
The mechanism of action of steroid hormones in target tissues include the binding of the steroid molecule to specific receptors in the cytoplasm. Steroid receptors may therefore be regarded as mediators of hormone action. The presence of such receptors in tissues reflects their hormone-sensitivity and the receptor levels are indicative of the relative potential for a direct hormonal action on the tissue in question. Using 3H-labeled synthetic ligands and a charcoal adsorption assay, the presence of specific androgen, glucocorticoid and estrogen (in rabbits only) receptors was demonstrated in human and rabbit skeletal muscle cytosol. These tissues can therefore be regarded as targets for these steroids. Scatchard analysis was then used to quantitate the receptors in muscle in different conditions. In back muscle of scoliotic patients, the concentrations of androgen and glucocorticoid receptors were similar on the convex and concave sides, except the concentration of glucocorticoid receptors (per g of wet weight), which was higher on the convex side. The tissue concentration (per g of wet weight) of glucocorticoid and estrogen receptors (but not of androgen receptor) was higher in rabbit soleus (slow-twitch) muscle than in the gastrocnemius/plantaris (fast-twitch) muscle complex. When the concentrations were related to the number of nuclei (i.e. expressed per mg of DNA), however, only the estrogen receptor concentration differed between the muscles (higher in soleus). Muscle atrophy in rabbit gastrocnemius muscle was induced by tenotomy or denervation and led to similar changes with an increase with time in androgen and glucocorticoid receptor levels (expressed per g of wet weight or per mg of protein) and a concomitant loss of muscle weight and protein. The total muscle content of receptors or the receptor concentration expressed per mg of DNA were also increased, but to a lesser extent. Synthetic anabolic-androgenic steroids can act directly on skeletal muscle in view of their capacity to bind to the androgen receptor as shown in the present study. Relative binding affinities of anabolic-androgenic steroids to the androgen receptor were similar in rabbit and rat skeletal muscle and in rat prostate. The protein/DNA ratio in the muscle samples was used as an estimation of the size of the "functional DNA-unit". The results indicate that slow-twitch fibers have smaller "DNA units", but also that muscle atrophy causes a decrease of the size of the "DNA unit".(ABSTRACT TRUNCATED AT 400 WORDS)
类固醇激素在靶组织中的作用机制包括类固醇分子与细胞质中的特定受体结合。因此，类固醇受体可被视为激素作用的介质。组织中此类受体的存在反映了它们对激素的敏感性，而受体水平则表明激素对相关组织直接作用的相对潜力。使用3H标记的合成配体和活性炭吸附分析法，在人和兔的骨骼肌胞质溶胶中证实了特异性雄激素、糖皮质激素和雌激素（仅在兔中）受体的存在。因此，这些组织可被视为这些类固醇的靶组织。然后使用Scatchard分析法定量不同条件下肌肉中的受体。在脊柱侧弯患者的背部肌肉中，雄激素和糖皮质激素受体的浓度在凸侧和凹侧相似，但糖皮质激素受体的浓度（每克湿重）在凸侧更高。兔比目鱼肌（慢肌纤维）中糖皮质激素和雌激素受体的组织浓度（每克湿重）高于腓肠肌/跖肌（快肌纤维）复合体，但雄激素受体的组织浓度在两者中无差异。然而，当浓度与细胞核数量相关时（即每毫克DNA表示），只有雌激素受体浓度在两种肌肉中有所不同（比目鱼肌中更高）。兔腓肠肌的肌肉萎缩通过切断肌腱或去神经支配诱导，导致雄激素和糖皮质激素受体水平（每克湿重或每毫克蛋白质表示）随时间增加，同时肌肉重量和蛋白质减少，且受体的总肌肉含量或每毫克DNA表示的受体浓度也增加，但增加程度较小。鉴于本研究中合成促合成代谢雄激素类固醇与雄激素受体结合的能力，它们可直接作用于骨骼肌。促合成代谢雄激素类固醇与雄激素受体的相对结合亲和力在兔和大鼠的骨骼肌以及大鼠前列腺中相似。肌肉样本中的蛋白质/DNA比值用作“功能性DNA单位”大小估计。结果表明，慢肌纤维具有较小的“DNA单位”，而且肌肉萎缩会导致“DNA单位”大小减小。（摘要截选至400字）
