Hanke C J, Drewett J G, Myers C R, Campbell W B
Department of Pharmacology and Toxicology, Medical College of Wisconsin, Milwaukee 53226, USA.
Endocrinology. 1998 Oct;139(10):4053-60. doi: 10.1210/endo.139.10.6252.
To investigate the mechanism of nitric oxide (NO) inhibition of aldosterone release, this study compared the effects of type A natriuretic peptide and heat-stable enterotoxin to a nitric oxide donor, deta nonoate, on cGMP production and angiotensin II-stimulated aldosterone synthesis ill primary cultures of bovine adrenal zona glomerulosa cells. Type A natriuretic peptide (10(-10)-10(-6) M) and deta nonoate (10(-6)-10(-3) M) stimulated concentration-related increases in cGMP production. Heat-stable enterotoxin (10(-6) M) failed to stimulate cGMP synthesis in zona glomerulosa cells. Type A natriuretic peptide and deta nonoate attenuated angiotensin II-stimulated aldosterone production over the same concentration range that stimulated cGMP production. Heat-stable enterotoxin (10(-6) M) was without effect on aldosterone release. To further test the hypothesis that cGMP mediated the inhibition of aldosterone synthesis, the selective inhibitor of soluble guanylyl cyclase, 1H-(1,2,4)oxadiazolo [4,3-a]quinoxalin-1-one (ODQ) was used. ODQ pretreatment (10(-5) M) completely prevented deta nonoate-stimulated cGMP production without altering the inhibitory effect of deta nonoate on angiotensin II-stimulated steroidogenesis. Consistent with its selectivity for inhibiting soluble guanylyl cyclase, ODQ did not block type A natriuretic peptide-stimulated cGMP synthesis or type A natriuretic peptide inhibition of steroidogenesis. Deta nonoate completely blocked 25-hydroxycholesterol- and progesterone-stimulated aldosterone synthesis in zona glomerulosa cells and inhibited the conversion of 25-hydroxycholesterol to pregnenolone in mitochondrial fractions from bovine adrenal cortex. Deta nonoate-derived NO gave an absorbance maximum of the mitochondrial cytochrome P450 of 453 nm and inhibited the absorbance at 450 nm caused by carbon monoxide binding to the enzyme. These results suggest that deta nonoate reduces steroidogenesis independent of guanylyl cyclase activation and that NO has a direct effect to inhibit the activity of cytochrome P450, probably by binding to the heme groups of the cytochrome.
为研究一氧化氮（NO）抑制醛固酮释放的机制，本研究比较了A型利钠肽和热稳定肠毒素与一氧化氮供体二乙三胺 NONO 酸盐对牛肾上腺球状带细胞原代培养物中cGMP生成及血管紧张素 II 刺激的醛固酮合成的影响。A型利钠肽（10⁻¹⁰ - 10⁻⁶ M）和二乙三胺 NONO 酸盐（10⁻⁶ - 10⁻³ M）刺激cGMP生成呈浓度相关增加。热稳定肠毒素（10⁻⁶ M）未能刺激球状带细胞中的cGMP合成。A型利钠肽和二乙三胺 NONO 酸盐在刺激cGMP生成的相同浓度范围内减弱血管紧张素 II 刺激的醛固酮生成。热稳定肠毒素（10⁻⁶ M）对醛固酮释放无影响。为进一步验证cGMP介导醛固酮合成抑制这一假说，使用了可溶性鸟苷酸环化酶的选择性抑制剂1H-(1,2,4)恶二唑并[4,3-a]喹喔啉-1-酮（ODQ）。ODQ预处理（10⁻⁵ M）完全阻止了二乙三胺 NONO 酸盐刺激的cGMP生成，同时不改变二乙三胺 NONO 酸盐对血管紧张素 II 刺激的类固醇生成的抑制作用。与其对抑制可溶性鸟苷酸环化酶的选择性一致，ODQ未阻断A型利钠肽刺激的cGMP合成或A型利钠肽对类固醇生成的抑制作用。二乙三胺 NONO 酸盐完全阻断了球状带细胞中25-羟胆固醇和孕酮刺激的醛固酮合成，并抑制了牛肾上腺皮质线粒体组分中25-羟胆固醇向孕烯醇酮的转化。二乙三胺 NONO 酸盐衍生的NO使线粒体细胞色素P450的最大吸光度在453 nm处，并抑制了一氧化碳与该酶结合引起的450 nm处的吸光度。这些结果表明，二乙三胺 NONO 酸盐降低类固醇生成与鸟苷酸环化酶激活无关，且NO可能通过与细胞色素的血红素基团结合直接抑制细胞色素P450的活性。
