CYTOPLASMIC PH REGULATION AND CHLORIDE BICARBONATE EXCHANGE IN AVIAN OSTEOCLASTS
CYTOPLASMIC PH REGULATION AND CHLORIDE BICARBONATE EXCHANGE IN AVIAN OSTEOCLASTS
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DOI：
10.1172/jci113863
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发表时间：
1989-01-01
影响因子：
15.9
通讯作者：
SCHLESINGER, PH
中科院分区：
文献类型：
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作者：
TETI, A;BLAIR, HC;SCHLESINGER, PH
破骨细胞通过首先附着到骨表面然后将质子分泌到在细胞-骨附着位点处形成的分离的细胞外隔室中来再吸收骨。这种质子分泌（局部酸化）是溶解骨羟基磷灰石晶体和骨胶原降解酸性蛋白酶活性所必需的。然而，所需的大量质子（2 mol/mol钙）将导致细胞溶质碱当量的等量积累。必须校正这种碱性负荷以将细胞溶质pH维持在生理限度内。在这项研究中，我们已经测量了细胞质pH值与pH敏感的荧光化合物，而不同的细胞外离子组成的介质，以确定的性质的补偿机制所使用的破骨细胞在骨吸收。我们的数据表明，破骨细胞具有氯离子/碳酸氢盐交换，使他们能够保持正常的细胞内pH值在面对一个显着的质子流出。这一结论来自于当已在含碳酸氢盐的培养基中孵育的破骨细胞转移到无碳酸氢盐的培养基中时，细胞质急剧酸化的证明。这种酸化完全依赖于介质[Cl-]并与介质[Cl-]成比例。此外，酸化被红细胞阴离子交换的经典抑制剂4，4“-二异硫氰基芪-2，2”-二磺酸盐和二苯胺-2-羧酸盐（一种氯特异性通道的抑制剂）抑制。然而，酸化过程既不依赖于能量也不依赖于钠。氯离子/碳酸氢根交换的生理重要性通过破骨细胞从内源性或外源性碱性负荷中恢复的氯离子依赖性来证明。我们的结论是，氯/碳酸氢盐交换是在很大程度上负责细胞质pH值的动态平衡的活性破骨细胞，这些细胞是类似的肾小管上皮细胞在其调节细胞内pH值。
Osteoclasts resorb bone by first attaching to the bone surface and then secreting protons into an isolated extracellular compartment formed at the cell-bone attachment site. This secretion of protons (local acidification) is required to solubilize bone hydroxyapatite crystals and for activity of bone collagen-degrading acid proteases. However, the large quantity of protons required, 2 mol/mol of calcium, would result in an equal accumulation of cytosolic base equivalents. This alkaline load must be corrected to maintain cytosolic pH within physiologic limits. In this study, we have measured cytoplasmic pH with pH-sensitive fluorescent compounds, while varying the extracellular ionic composition of the medium, to determine the nature of the compensatory mechanism used by osteoclasts during bone resorption. Our data show that osteoclasts possess a chloride/bicarbonate exchanger that enables them to maintain normal intracellular pH in the face of a significant proton efflux. This conclusion follows from the demonstration of a dramatic cytoplasmic acidification when osteoclasts that have been incubated in bicarbonate-containing medium are transferred into bicarbonate-free medium. This acidification is absolutely dependent on and proportional to medium [Cl-]. Furthermore, acidification is inhibited by the classic inhibitor of red cell anion exchange, 4,4''-diisothiocyanatostilbene-2,2''-disulfonate, and by diphenylamine-2-carboxylate, an inhibitor of chloride specific channels. However, the acidification process is neither energy nor sodium dependent. The physiologic importance of chloride/bicarbonate exchange is demonstrated by the chloride dependence of recovery from an endogenous or exogenous alkaline load in osteoclasts. We conclude that chloride/bicarbonate exchange is in large part responsible for cytoplasmic pH homeostasis of active osteoclasts, showing that these cells are similar to renal tubular epithelial cells in their regulation of intracellular pH.