Chavarri M R, Yamakita N, Chiou S, Gomez-Sanchez C E
Department of Internal Medicine, University of South Florida Health Sciences Center, Tampa.
J Steroid Biochem Mol Biol. 1993 Jun;45(6):493-500. doi: 10.1016/0960-0760(93)90164-r.
Aldosterone production occurs in the outer area of the adrenal cortex, the zona glomerulosa. The glucocorticoids cortisol and corticosterone, depending upon the species, are synthesized in the inner cortex, the zona fasciculata. Calf zona glomerulosa cells rapidly lose the ability to synthesize aldosterone when placed in primary culture unless they are incubated in the presence of the antioxidants butylated hydroxyanisol and selenous acid, the radioprotectant DMSO, and the cytochrome P-450 inhibitor metyrapone. In the presence of these additives, calf zona fasciculata cells in primary culture synthesize aldosterone at rates which can approach those from cells isolated from the zona glomerulosa. Calf zona glomerulosa and fasciculata cells both responded well to ACTH and angiotensin II, but the zona fasciculata cells respond very poorly compared to glomerulosa cells to increased potassium in the media. Rat zona fasciculata cells in primary culture under similar conditions did not synthesize aldosterone, suggesting that the regulation of the expression of the enzymes responsible for the biosynthesis of aldosterone in the two species is different. Two distinct cytochrome P-450 cDNAs which hydroxylate deoxycorticosterone at the 11 beta position have been described in the rat, human and mouse. Both cytochrome P-450 cDNAs have been cloned and expressed in non-steroidogenic cells, but only one is expressed in the zona glomerulosa and only this glomerulosal cytochrome P450 can further hydroxylate deoxycorticosterone to generate aldosterone. Two bovine adrenal cDNAs have been described with 11 beta-hydroxylase activity and their expression products in transiently transfected COS cells can convert deoxycorticosterone into aldosterone. Both enzymes are expressed in all zones of the adrenal cortex. Zonal regulation of aldosterone synthesis in the bovine adrenal gland may be due to an 11 beta-hydroxylase with aldosterone synthesizing capacity which has not yet been isolated. Alternatively, a single enzyme might be responsible for the several hydroxylations in the pathway between deoxycorticosterone and aldosterone and zonal synthesis might be controlled by unknown factors regulating the expression of C-18 hydroxylation. The incubation of zona fasciculata with antioxidants and metyrapone results in atypical expression of this activity by an unclear mechanism.
醛固酮在肾上腺皮质的外层即球状带产生。糖皮质激素皮质醇和皮质酮（因物种而异）在肾上腺皮质内层即束状带合成。小牛的球状带细胞在原代培养时，若不与抗氧化剂丁基羟基茴香醚和亚硒酸、辐射防护剂二甲基亚砜以及细胞色素P - 450抑制剂美替拉酮一起孵育，会迅速丧失合成醛固酮的能力。在这些添加剂存在的情况下，原代培养的小牛束状带细胞合成醛固酮的速率可接近从球状带分离的细胞的合成速率。小牛的球状带和束状带细胞对促肾上腺皮质激素（ACTH）和血管紧张素II均反应良好，但与球状带细胞相比，束状带细胞对培养基中钾离子增加的反应非常弱。在类似条件下，原代培养的大鼠束状带细胞不合成醛固酮，这表明这两个物种中负责醛固酮生物合成的酶的表达调控存在差异。在大鼠、人类和小鼠中已发现两种不同的细胞色素P - 450 cDNA，它们可在11β位将脱氧皮质酮羟化。这两种细胞色素P - 450 cDNA均已被克隆并在非类固醇生成细胞中表达，但只有一种在球状带表达，且只有这种球状带细胞色素P450能进一步将脱氧皮质酮羟化生成醛固酮。已描述了两种具有11β - 羟化酶活性的牛肾上腺cDNA，它们在瞬时转染的COS细胞中的表达产物可将脱氧皮质酮转化为醛固酮。这两种酶在肾上腺皮质的所有区域均有表达。牛肾上腺中醛固酮合成的区域调控可能是由于一种尚未分离出来的具有醛固酮合成能力的11β - 羟化酶。或者，单一酶可能负责脱氧皮质酮和醛固酮之间途径中的几种羟化反应，区域合成可能受调控C - 18羟化表达的未知因素控制。用抗氧化剂和美替拉酮孵育束状带会通过不明机制导致这种活性的非典型表达。
