Kino M, Tokushige A, Tamura H, Hopp L, Searle B M, Khalil F, Aviv A
Am J Physiol. 1985 May;248(5 Pt 1):C436-41. doi: 10.1152/ajpcell.1985.248.5.C436.
This study explores the relationship between extracellular calcium (Cao) and Na+-K+ regulation as it particularly pertains to the activity of the Na+ pump in cultured vascular smooth muscle cells (VSMCs) originating from Sprague-Dawley rats. As compared with cells incubated in media containing 0.5, 2.0, or 4.0 mM calcium, when the Na pump is active, VSMCs incubated in a Ca-deficient medium show a marked increase in intracellular sodium and no significant change in intracellular potassium. Associated with the rise in intracellular sodium there is an augmented activity of the Na pump. When the Na pump is inhibited, VSMCs incubated in either high-Ca medium (Cao = 4.0 mM) or Ca-deficient medium manifest a greater decline in intracellular potassium than cells incubated in media containing 0.5 or 2.0 mM calcium. Furthermore, when the Na pump is inhibited, VSMCs incubated in a Ca-deficient medium exhibit higher intracellular sodium levels in comparison with their counterparts incubated in media containing calcium. Flux experiments indicate that the aforementioned changes reflect increased membrane permeabilities to Na+ and K+. It is concluded that by regulating the permeability of the VSMC membrane, Cao plays an important role in the intracellular Na+-K+ homeostasis and that its effect on the Na pump is mediated via perturbations in the intracellular Na+ and K+ concentrations.
本研究探讨细胞外钙（Caₒ）与Na⁺-K⁺调节之间的关系，尤其涉及源自Sprague-Dawley大鼠的培养血管平滑肌细胞（VSMC）中Na⁺泵的活性。与在含有0.5、2.0或4.0 mM钙的培养基中孵育的细胞相比，当Na泵活跃时，在缺钙培养基中孵育的VSMC细胞内钠显著增加，而细胞内钾无明显变化。随着细胞内钠的升高，Na泵的活性增强。当Na泵被抑制时，在高钙培养基（Caₒ = 4.0 mM）或缺钙培养基中孵育的VSMC细胞内钾的下降幅度比在含有0.5或2.0 mM钙的培养基中孵育的细胞更大。此外，当Na泵被抑制时，与在含钙培养基中孵育的VSMC相比，在缺钙培养基中孵育的VSMC细胞内钠水平更高。通量实验表明，上述变化反映了细胞膜对Na⁺和K⁺的通透性增加。结论是，通过调节VSMC膜的通透性，Caₒ在细胞内Na⁺-K⁺稳态中起重要作用，并且其对Na泵的影响是通过细胞内Na⁺和K⁺浓度的扰动介导的。
