Mobasheri A
University Laboratory of Physiology, University of Oxford, United Kingdom.
Physiol Res. 1998;47(1):47-52.
The plasma membrane abundance of the Na+/K+ pump or Na+,K+-ATPase depends on the intracellular concentration of Na+ in almost all animal cells. In cartilage, chondrocytes are surrounded by an extracellular matrix which consists of collagen and proteoglycan, a ground substance composed of glycosaminoglycan (GAG) side chains with a high fixed negative charge density. The polyanionic nature of the GAGs tends to draw monovalent cations into the matrix resulting in high [Na+] which may exceed 250 mM. As the concentration of GAGs in the tissue increases, so does [Na+]. In this study, it was found that the density of the Na+/K+ pump, measured by 3H-ouabain binding, correlates with the concentration of GAGs in the tissue. This indicates that chondrocytes are sensitive to their ionic environment and respond to local [Na+] variations by regulating the abundance of the Na+/K+ pump.
在几乎所有动物细胞中，钠钾泵（即Na⁺,K⁺-ATP酶）在质膜上的丰度取决于细胞内的钠离子浓度。在软骨中，软骨细胞被细胞外基质所包围，该基质由胶原蛋白和蛋白聚糖组成，后者是一种由糖胺聚糖（GAG）侧链构成的基质，带有高固定负电荷密度。GAG的聚阴离子性质倾向于将单价阳离子吸引到基质中，导致细胞外基质中钠离子浓度升高，可能超过250 mM。随着组织中GAG浓度的增加，钠离子浓度也会升高。在本研究中，通过³H-哇巴因结合法测得的钠钾泵密度与组织中GAG的浓度相关。这表明软骨细胞对其离子环境敏感，并通过调节钠钾泵的丰度来响应局部钠离子浓度的变化。
