Muto S, Nemoto J, Ebata S, Kawakami K, Asano Y
Department of Nephrology, Jichi Medical School, Tochigi, Japan.
Kidney Int. 1998 Aug;54(2):492-508. doi: 10.1046/j.1523-1755.1998.00033.x.
In mineralocorticoid target tissues such as kidney and colon, the enzyme 11 beta-hydroxysteroid dehydrogenase (11 beta OHSD) catalizes the reversible conversion of corticosterone (CS) to inactive 11-dehydrocorticosterone (DHCS) in rats, and cortisol to inactive cortisone in humans. This enzyme is also expressed in vascular smooth muscle cells (VSMC).
In cultured VSMC from rat thoracic aortae, we examined the effects of CS and DHCS on Na,K-ATPase alpha 1- and beta 1-mRNA accumulation by Northern blot analysis, on alpha 1- and beta 1-subunit protein accumulation by Western blot analysis, and on Na,K-ATPase activity by the coupled assay method.
In VSMC, CS and DHCS (10(-6) M) increased alpha 1-mRNA level 2.6- and 2.5-fold at 48 hours and beta 1-mRNA level 9.2- and 9.1-fold at 12 hours, respectively. The RNA transcription inhibitor (actinomycin D) abolished both CS- and DHCS-mediated alpha 1- and beta 1-mRNA induction. The glucocorticoid receptor antagonist (RU38486) and the mineralocorticoid receptor antagonists (ZK91587) inhibited both CS- and DHCS-mediated alpha 1- and beta 1-mRNA induction. The 11 beta OHSD inhibitor (carbenoxolone) inhibited DHCS-mediated alpha 1- and beta 1-mRNA induction, whereas it caused no effect on CS-mediated alpha 1- or beta 1-mRNA induction. The addition of CS or DHCS to VSMC significantly increased alpha 1- and beta 1-subunit protein levels and Na,K-ATPase activity. When adrenalectomized rats were treated with CS or DHCS for 12 hours, aorta alpha 1- and beta 1-mRNA levels increased 3.0- and 8.7-fold or 3.4- and 8.4-fold, respectively.
In VSMC, both CS and DHCS stimulate Na,K-ATPase alpha 1- and beta 1-mRNA accumulation, alpha 1- and beta 1-subunit protein accumulation, and Na,K-ATPase activity. The CS-mediated alpha 1- and beta 1-mRNA induction occurs independently of 11 beta OHSD, whereas the DHCS-mediated alpha 1- and beta 1-mRNA induction occurs through 11 beta OHSD-dependent mechanisms, possibly via conversion of inactive DHCS into active CS.
在盐皮质激素作用的靶组织如肾脏和结肠中，11β-羟基类固醇脱氢酶（11βOHSD）催化大鼠体内皮质酮（CS）可逆转化为无活性的11-脱氢皮质酮（DHCS），在人类体内催化皮质醇转化为无活性的可的松。该酶也在血管平滑肌细胞（VSMC）中表达。
在来自大鼠胸主动脉的培养VSMC中，我们通过Northern印迹分析检测CS和DHCS对Na，K-ATP酶α1和β1 mRNA积累的影响，通过Western印迹分析检测对α1和β1亚基蛋白积累的影响，并通过偶联测定法检测对Na，K-ATP酶活性的影响。
在VSMC中，CS和DHCS（10⁻⁶ M）分别在48小时时使α1 mRNA水平增加2.6倍和2.5倍，在12小时时使β1 mRNA水平增加9.2倍和9.1倍。RNA转录抑制剂（放线菌素D）消除了CS和DHCS介导的α1和β1 mRNA诱导。糖皮质激素受体拮抗剂（RU38486）和盐皮质激素受体拮抗剂（ZK91587）抑制了CS和DHCS介导的α1和β1 mRNA诱导。11βOHSD抑制剂（生胃酮）抑制了DHCS介导的α1和β1 mRNA诱导，而对CS介导的α1或β1 mRNA诱导没有影响。向VSMC中添加CS或DHCS显著增加了α1和β1亚基蛋白水平以及Na，K-ATP酶活性。当对肾上腺切除的大鼠用CS或DHCS处理12小时时，主动脉α1和β1 mRNA水平分别增加3.0倍和8.7倍或3.4倍和8.4倍。
在VSMC中，CS和DHCS均刺激Na，K-ATP酶α1和β1 mRNA积累、α1和β1亚基蛋白积累以及Na，K-ATP酶活性。CS介导的α1和β1 mRNA诱导独立于11βOHSD发生，而DHCS介导的α1和β1 mRNA诱导通过11βOHSD依赖性机制发生，可能是通过将无活性的DHCS转化为活性CS。
