Siegel G, Walter A, Gustavsson H, Lindman B
Artery. 1981;9(3):232-52.
Since a tight electromechanical coupling exists in vascular smooth muscle, even small shifts of the membrane potential are sufficient to change the vascular lumen. The extracellular H+ and K+ concentrations are important effectors for the adjustment of the membrane potential. The ion concentrations in the immediate neighbourhood of the cell membrane can be influenced by the microdynamic binding properties of the basement membrane and the other vascular connective tissue. These structures are polyanionic macromolecules to which mono- and divalent cations are extensively bound, and which are separated from the vascular smooth muscle cell membranes by tiny cleft spaces. The ion binding properties of vascular connective tissue were therefore studied in dependence on proton and cation concentration. The pH-dependent binding of monovalent cations to vascular connective tissue is dependent on the concentration and affinity constant of the ion species in question. The mode of interaction is competition. For instance, the actual K binding characteristic means that an increase of [K+]o close to the cell membrane cold ensue from a diminished K+ binding ability under alkalosis. Depolarization and contraction of vascular smooth muscle cells result. Divalent cation binding to vascular connective tissue it additionally dependent on conformational changes. Already physiological concentrations of Mg++ ions can induce a specific change in configuration, which enables K+ ions to bind cooperatively. This means that with extracellular Mg++ deficiency not only less Mg++ ions are bound to vascular connective tissue but also less K+ ions. [K+]o would increase near the cell membrane, depolarization and vasoconstriction would occur.
由于血管平滑肌中存在紧密的机电耦合，即使膜电位的微小变化也足以改变血管腔。细胞外H⁺和K⁺浓度是调节膜电位的重要效应器。细胞膜紧邻区域的离子浓度可受基底膜和其他血管结缔组织的微动态结合特性影响。这些结构是多阴离子大分子，一价和二价阳离子与之广泛结合，且通过微小的裂隙空间与血管平滑肌细胞膜分隔开。因此，研究了血管结缔组织的离子结合特性与质子和阳离子浓度的关系。一价阳离子与血管结缔组织的pH依赖性结合取决于相关离子种类的浓度和亲和常数。相互作用模式为竞争。例如，实际的K结合特性意味着在碱中毒时，由于K⁺结合能力减弱，靠近细胞膜的[K⁺]o会增加。导致血管平滑肌细胞去极化和收缩。二价阳离子与血管结缔组织的结合还取决于构象变化。生理浓度的Mg²⁺离子就能诱导特定的构象变化，使K⁺离子能协同结合。这意味着细胞外Mg²⁺缺乏时，不仅与血管结缔组织结合的Mg²⁺离子减少，K⁺离子也减少。细胞膜附近的[K⁺]o会增加，会发生去极化和血管收缩。
