Jaspers S R, Henriksen E, Jacob S, Tischler M E
Department of Biochemistry, University of Arizona, Tucson 85724.
Metabolism. 1989 Feb;38(2):109-14. doi: 10.1016/0026-0495(89)90248-5.
Degradation of branched-chain amino acids was studied in muscles of unloaded hind limbs from rats subjected to six days of tail-cast suspension. The total production of 14CO2 from uniformly labeled 14C-leucine, isoleucine, or valine, and the fluxes through leucine aminotransferase and alpha-ketoisocaproate dehydrogenase, which were measured using L-1-14C-leucine, were generally greater in the soleus and extensor digitorum longus muscles of unloaded than of weight-bearing hind limbs. Adrenalectomy abolished any difference in flux through the aminotransferase, whereas the administration of cortisol to adrenalectomized animals restored the greater flux in the unloaded soleus muscle. Adrenalectomy partially diminished the greater flux through alpha-ketoisocaproate dehydrogenase in the unloaded soleus, whereas cortisol (2 mg/100 g body weight) treatment increased this difference. In the extensor digitorum longus, adrenalectomy abolished the differences in both enzyme fluxes due to hind limb suspension. In this muscle, cortisol treatment increased these fluxes to a similar extent in both weight-bearing and suspended, adrenalectomized animals so that the normal difference was not restored. These results suggest that leucine catabolism in hind limb muscles of suspended rats was influenced primarily by increased circulating glucocorticoid hormones, which are elevated twofold to fourfold in these animals.
对经六天尾部悬吊的大鼠后肢去负荷肌肉中支链氨基酸的降解情况进行了研究。用均匀标记的¹⁴C-亮氨酸、异亮氨酸或缬氨酸产生的¹⁴CO₂总量，以及使用L-1-¹⁴C-亮氨酸测量的通过亮氨酸转氨酶和α-酮异己酸脱氢酶的通量，在去负荷的比目鱼肌和趾长伸肌中通常比负重后肢的更大。肾上腺切除术消除了通过转氨酶的通量差异，而给肾上腺切除的动物注射皮质醇可恢复去负荷比目鱼肌中更大的通量。肾上腺切除术部分降低了去负荷比目鱼肌中通过α-酮异己酸脱氢酶的更大通量，而皮质醇（2毫克/100克体重）处理增加了这种差异。在趾长伸肌中，肾上腺切除术消除了因后肢悬吊导致的两种酶通量差异。在该肌肉中，皮质醇处理在负重和悬吊的肾上腺切除动物中使这些通量增加到相似程度，因此未恢复正常差异。这些结果表明，悬吊大鼠后肢肌肉中的亮氨酸分解代谢主要受循环糖皮质激素增加的影响，这些动物的循环糖皮质激素升高了两倍至四倍。
