Djouadi F, Wijkhuisen A, Bastin J, Vilar J, Merlet-Bénichou C
INSERM U319, Université Paris 7, France.
Ren Physiol Biochem. 1993 Sep-Oct;16(5):249-56. doi: 10.1159/000173770.
The activities of three mitochondrial oxidative enzymes (citrate synthase, 3-ketoacid-CoA transferase, beta-hydroxyacyl-CoA dehydrogenase) and Na-K-ATPase were microassayed in isolated segments of the rat proximal convoluted tubule (PCT) and medullary thick ascending limb of the loop of Henle (mTAL). The effects of adrenalectomy (ADX) and ADX plus exogenous glucocorticoids were analyzed. The hormonal replacement was daily injections of dexamethasone (10 micrograms/100 g body weight/24 h) for 5 days. ADX lowered the activity of all oxidative enzymes studies in the mTAL, but not in the PCT and led to a decrease in Na-K-ATPase in both nephron segments. Dexamethasone restored the normal level of oxidative enzymes and Na-K-ATPase in the mTAL and of Na-K-ATPase in the PCT. We conclude that the activities of citrate synthase, 3-ketoacid-CoA transferase and beta-hydroxyacyl-CoA dehydrogenase and of Na-K-ATPase are coordinately regulated in the mTAL and that glucocorticoids are essential for the long-term regulation of these enzyme activities in this nephron segment. In contrast, the activities of mitochondrial oxidative enzymes are not influenced by glucocorticoids in the PCT. This study presents the first evidence for a cell-specific regulation by glucocorticoids of oxidative metabolism in the nephron of adult rat kidney.
在大鼠近端肾小管（PCT）和髓袢升支粗段（mTAL）的分离节段中，对三种线粒体氧化酶（柠檬酸合酶、3-酮酸-CoA转移酶、β-羟酰基辅酶A脱氢酶）和钠钾ATP酶的活性进行了微量测定。分析了肾上腺切除术（ADX）以及ADX加外源性糖皮质激素的影响。激素替代治疗为连续5天每日注射地塞米松（10微克/100克体重/24小时）。ADX降低了mTAL中所有所研究氧化酶的活性，但对PCT中的氧化酶活性没有影响，并且导致两个肾单位节段中的钠钾ATP酶活性降低。地塞米松使mTAL中氧化酶和钠钾ATP酶的水平恢复正常，并使PCT中钠钾ATP酶的水平恢复正常。我们得出结论，在mTAL中，柠檬酸合酶、3-酮酸-CoA转移酶、β-羟酰基辅酶A脱氢酶以及钠钾ATP酶的活性受到协同调节，并且糖皮质激素对于该肾单位节段中这些酶活性的长期调节至关重要。相比之下，PCT中线粒体氧化酶的活性不受糖皮质激素的影响。本研究首次证明了糖皮质激素对成年大鼠肾脏肾单位氧化代谢的细胞特异性调节作用。
