Oguchi A, Ikeda U, Kanbe T, Tsuruya Y, Yamamoto K, Kawakami K, Medford R M, Shimada K
Department of Cardiology, Jichi Medical School, Tochigi, Japan.
Am J Physiol. 1993 Oct;265(4 Pt 2):H1167-72. doi: 10.1152/ajpheart.1993.265.4.H1167.
Na-K-adenosinetriphosphatase (ATPase) activity profoundly influences vascular cell excitability, contractility, and volume regulation. The recent finding of mineralocorticoid hormone receptors in vascular tissue suggests the possibility that Na-K-ATPase gene expression in vascular tissue is regulated by the mineralocorticoid aldosterone. In this study, we investigated Na-K-ATPase gene expression by aldosterone in cultured rat vascular smooth muscle cells (VSMC). Na-K-ATPase alpha 1- and beta 1-isoform mRNAs, but not alpha 2- and alpha 3-isoform mRNAs, were expressed in cultured rat VSMC. Aldosterone caused a 2.3-fold increase in the alpha 1 mRNA and a 4.7-fold increase in the beta 1 mRNA accumulation with peak elevations at 24 and 6 h, respectively. Aldosterone induced the alpha 1 mRNA expression at physiological concentrations (half-maximum effective concentration = 2-3 nM), consistent with the binding of aldosterone to mineralocorticoid hormone receptors. The augmented alpha 1 mRNA expression by aldosterone was associated with a twofold increase in the alpha 1-subunit protein accumulation. Pretreatment of VSMC with cycloheximide caused a 10-fold increase in the alpha 1 mRNA expression, and the aldosterone-mediated alpha 1 mRNA accumulation was not observed in the presence of cycloheximide. Transfection experiments with the luciferase reporter gene revealed that aldosterone response sequences are located within the 5'-flanking regions of the alpha 1-isoform gene. These data demonstrate that the mineralocorticoid aldosterone directly stimulates Na-K-ATPase gene expression and protein accumulation in VSMC.
钠钾 - 三磷酸腺苷酶（ATP酶）活性深刻影响血管细胞的兴奋性、收缩性和容量调节。近期在血管组织中发现盐皮质激素受体提示了血管组织中钠钾ATP酶基因表达可能受盐皮质激素醛固酮调节的可能性。在本研究中，我们调查了醛固酮对培养的大鼠血管平滑肌细胞（VSMC）中钠钾ATP酶基因表达的影响。培养的大鼠VSMC中表达钠钾ATP酶α1和β1亚型的mRNA，但不表达α2和α3亚型的mRNA。醛固酮使α1 mRNA增加2.3倍，β1 mRNA积累增加4.7倍，峰值分别出现在24小时和6小时。醛固酮在生理浓度下（半数最大有效浓度 = 2 - 3 nM）诱导α1 mRNA表达，这与醛固酮与盐皮质激素受体的结合一致。醛固酮增强的α1 mRNA表达与α1亚基蛋白积累增加两倍相关。用放线菌酮预处理VSMC导致α1 mRNA表达增加10倍，并且在存在放线菌酮的情况下未观察到醛固酮介导的α1 mRNA积累。用荧光素酶报告基因进行的转染实验表明，醛固酮反应序列位于α1亚型基因的5'侧翼区域内。这些数据表明，盐皮质激素醛固酮直接刺激VSMC中钠钾ATP酶基因表达和蛋白积累。
