Properties of Aldosterone Synthase and the Regulation Mechanism in Adrenocortex.

尽管许多研究表明ALD的分泌受多种因素的控制，如ACTH、肾素-血管紧张素系统、Na~(++)和K~(++)等，但这些因素之间的相互关系及其调节机制仍未解决。这在很大程度上是因为催化ALD形成的最后一步的酶不明确。最近的研究表明，纯化的细胞色素P-45011除了具有11-和18-羟基化类固醇的内在活性外，还具有由脱氧皮质酮或皮质酮形成醛固酮的活性，尽管很弱。然而，这一观察结果并不能满足目前所获得的许多其他观察结果，如Z-肾小球(Z.G)的ALD分泌受限，以及ALD形成过程中存在遗传性缺陷而没有11-羟基酶活性缺陷的患者等。因此，我们研究了肾上腺皮质…线粒体部分中DOC转化为ALD过程中个别反应的活性本研究旨在从牛和大鼠肾上腺皮质线粒体中分离和鉴定ALD合酶。结果表明：1)Z.G的完整线粒体比Z.FR的完整线粒体产生更多的ALD，表现出明显的区带特异性。当两个区域的线粒体被超声作用时，活性变得相似，这表明区带特异性降低，Z.G线粒体的完整性对于正常的ALD产生是必不可少的。2)缺钠和补钾大鼠Z.G线粒体将DOC或COR转化为18-OHCOR和ALD的比率比缺钾和补钠大鼠高几到十倍。然而，相同的制备方法在DOC.3的11-羟基化和18-羟基化方面几乎没有差异)新的P-450物种49K蛋白仅出现在刺激ALD生物合成的大鼠Z.G的线粒体中。4)我们用高效液相色谱-羟基磷灰石柱层析从缺钠大鼠Z.G中纯化了具有强大的ALD合成活性的49K蛋白。该酶与51K蛋白(真正的细胞色素P-45011)完全分离，命名为ALD合成酶。ALD生物合成的各种诱导剂对49K蛋白的诱导目前正在实验室进行中。较少

Although a number of studies to date indicate that secretion of albosterone (ALD) is controlled by verious factors,such as ACTH,renin-angiotensin system,Na^+ and K^+,the interrelationship among these factors and the regulatory mechanism remain unresolved. This is mostly because of ambiguity of the enzyme which catalyzed the final step of ALD formation. Recent works have shown that purified cytochrome P-45011 has the activity of ALD formation from deoxycorticosterone (DOC) or corticosterone (COR), although very weak, besides intrinsic activities of 11 - and 18-hybroxylation of steroids. Such an observation,however,does not satisfy with many other observations so far obtained like ALD secretion limited in z-glomerulosa (z.G) and the presence of patients with inherited defect in ALD formation without deficiency in 11 -hydroxylase activity so on. We therefore incestigated the activities of individual reactions during the conversion of DOC to ALD in mitochondrial fractions of adrenocortical … More z.G and z.fasciculata (z.FR) of cow or rat under normal or abnormal physiological conditions,and then intended to isolate and characterize ALD synthase from bovine and rat adrenocortical mitochondria. Results we obtained were as follows:1) The intact mitochondria from z.G could produce more ALD than those from z.FR, showing distinct zonal specificity of ALD biosynthesis. When the mitochondria from both zones were sonicated, the activity became similar with each other, indicating the zonal specificity diminished and the integrity of the z.G mitochondria was essential to normal ALD production.2) Mitochondria from z.G of Na-depleted and K-repleted rats converted DOC or COR to 18-OH COR and ALD at several-to ten-fold higher retes than those of K-depleted and Na-repleted rats. However,the same preparations exhibited almost no difference in the 11 -and 18-hydroxylation of DOC.3) New P-450 species,49K protein,appeared in mitochondria only from z.G of rats with stimulated ALD biosynthesis.4) We purified 49K protein with a potent ALD synthesis activity from z.G of Na-depleted rats using HPLC hydroxylapatite column. This was completely separated from 51K protein (genuine cytochrome p-45011 ) and was designated as ALD synthase. The induction of 49K protein by various ftimuli of ALD biosynthesisare now in progress in our labolatory. Less