Effect of calcium ions on steroid-binding spectra and pregnenolone formation in rat-adrenal mitochondria.
Effect of calcium ions on steroid-binding spectra and pregnenolone formation in rat-adrenal mitochondria.
复制标题
钙离子对大鼠肾上腺线粒体中类固醇结合谱和孕烯醇酮形成的影响。
DOI：
10.1111/j.1432-1033.1974.tb03542.x
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发表时间：
1974
期刊：
影响因子：
--
通讯作者：
G. S. Boyd
中科院分区：
文献类型：
--
作者：
E. Simpson;C. Jefcoate;J. McCARTHY;G. S. Boyd
在大鼠肾上腺线粒体中研究了钙离子对类固醇诱导的细胞色素P-450差谱和对双烯醇酮形成的影响。在磷酸盐的存在下，除了氯化钙的悬浮液中的这些线粒体导致在倒置的I型差异谱的增加，诱导的双烯醇酮或methylandrostenediol，和消失的I型光谱诱导的25-羟基胆固醇。醚应激动物和放线菌酮的线粒体之间的倒置I型光谱的差异被取消。胆固醇侧链裂解增加，提供NADPH发生器用作还原当量的来源。醚应激动物和放线菌酮给药动物的线粒体之间侧链裂解活性的差异得以维持。
在不存在磷酸盐的情况下，加入氯化钙再次导致由25-羟基胆固醇诱导的I型差异光谱的损失，但这一次在乙醚麻醉的大鼠线粒体中，由双烯醇酮诱导的倒置I型光谱几乎没有变化，而环己酰亚胺处理的大鼠的变化仅为约50%，25-羟基胆固醇诱导的差异光谱的变化。这些观察结果被解释在与侧链裂解提出存在于完整的肾上腺线粒体中的各种形式的细胞色素P-450的相互转化。
如牛血清白蛋白和EDTA，这增加了这些线粒体中的呼吸控制的因素，也刺激胆固醇侧链裂解活性，镁离子，但不改变类固醇结合光谱的大小。
The effect of calcium ions on steroid-induced difference spectra of cytochrome P-450, and on pregnenolone formation, has been studied in rat adrenal mitochondria. In the presence of phosphate, addition of calcium chloride to suspensions of these mitochondria resulted in an increase in the inverted type-I difference spectrum induced by pregnenolone or methylandrostenediol, and a disappearance of the type I spectrum induced by 25-hydroxycholesterol. The difference in the inverted type I spectrum between mitochondria from ether-stressed animals and those given cycloheximide was abolished. Cholesterol side-chain cleavage was increased, providing an NADPH generator was used as source of reducing equivalents. The difference in side-chain cleavage activity between mitochondria from ether-stressed animals and those given cycloheximide, was maintained.
In the absence of phosphate, addition of calcium chloride again resulted in a loss of the type I difference spectrum induced by 25-hydroxycholesterol, but this time there was almost no change in the inverted type I spectrum induced by pregnenolone in mitochondria from rats subjected to ether anaesthesia, and the change in cycloheximide-treated rats was only about 50%, of the change in the 25-hydroxycholesterol-induced difference spectrum. These observations are interpreted in terms of interconversions of the various forms of cytochrome P-450 associated with side-chain cleavage proposed to exist in intact adrenal mitochondria.
Factors such as bovine serum albumin and EDTA, which increase respiratory control in these mitochondria, also stimulate cholesterol side-chain cleavage activity, as do magnesium ions, but without altering the magnitude of the steroid-binding spectra.