Orlov S N, Tremblay J, Hamet P
Centre de Recherche Hôtel-Dieu de Montréal, Université de Montreal, Quebec, Canada.
Am J Physiol. 1996 May;270(5 Pt 1):C1388-97. doi: 10.1152/ajpcell.1996.270.5.C1388.
Vascular smooth muscle cells (VSMC) exhibit shrinkage-induced bumetanide-inhibited 86Rb influx and ethylisopropylamiloride (EIPA)-inhibited 22Na influx. In this study, we examined the role of these transport pathways in volume adjustment of VSMC after isosmotic and hyperosmotic shrinkage. Cell volume was assessed by measurement of [14C]urea distribution. An initial 18-20% cell volume decrease in isosmotically shrunken VSMC was followed by a regulatory volume increase (RVI). RVI was completely abolished by bumetanide but not by EIPA. No RVI was noted in hyperosmotically shrunken VSMC. The initial rate of bumetanide-inhibited 86Rb influx was two- to threefold higher in isosmotically shrunken VSMC than with hyperosmotic shrinkage. Hyperosmotic shrinkage of VSMC was accompanied by a three- to fourfold increase in the rate of bumetanide-inhibited 86Rb efflux, whereas isosmotic shrinkage augmented this component by only 20-30%. In contrast to bumetanide-inhibited 86Rb influx, isosmotic shrinkage slightly increased the rate of EIPA-sensitive 22Na influx. Hyperosmotic shrinkage led to transient activation of EIPA-inhibited 22Na influx, which was completely abolished in 15 min. Activation of adenosine 3',5'-cyclic monophosphate (cAMP) signaling with isoproterenol arborized VSMC and decreased their volume by approximately 15%. A similar volume decrease was seen in VSMC treated with the microfilament-disrupting compound, cytochalasin B. The isoproterenol-induced cell volume decrease was prolonged by the addition of bumetanide. Unlike isoproterenol, agents that raise intracellular Ca2+ (A-23187 and angiotensin II) did not modify VSMC volume. Thus our data demonstrate involvement of cAMP signaling in the regulating of VSMC volume and a key role of bumetanide-inhibited ion transport in the RVI after isosmotically induced shrinkage.
血管平滑肌细胞（VSMC）表现出收缩诱导的布美他尼抑制的⁸⁶Rb内流和乙基异丙基amiloride（EIPA）抑制的²²Na内流。在本研究中，我们研究了这些转运途径在等渗和高渗收缩后VSMC体积调节中的作用。通过测量[¹⁴C]尿素分布来评估细胞体积。等渗收缩的VSMC最初细胞体积减少18 - 20%，随后出现调节性体积增加（RVI）。布美他尼可完全消除RVI，但EIPA不能。在高渗收缩的VSMC中未观察到RVI。等渗收缩的VSMC中布美他尼抑制的⁸⁶Rb内流的初始速率比高渗收缩时高两到三倍。VSMC的高渗收缩伴随着布美他尼抑制的⁸⁶Rb外流速率增加三到四倍，而等渗收缩仅使该成分增加20 - 30%。与布美他尼抑制的⁸⁶Rb内流相反，等渗收缩略微增加了EIPA敏感的²²Na内流速率。高渗收缩导致EIPA抑制的²²Na内流短暂激活，15分钟后完全消除。用异丙肾上腺素激活腺苷3',5'-环磷酸（cAMP）信号通路使VSMC分支并使其体积减少约15%。在用微丝破坏化合物细胞松弛素B处理的VSMC中也观察到类似的体积减少。添加布美他尼可延长异丙肾上腺素诱导的细胞体积减少。与异丙肾上腺素不同，升高细胞内Ca²⁺的试剂（A - 23187和血管紧张素II）不会改变VSMC体积。因此，我们的数据表明cAMP信号通路参与VSMC体积调节，并且布美他尼抑制的离子转运在等渗诱导收缩后的RVI中起关键作用。
