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首页> 外文期刊>Journal of Cellular Physiology >High capacity Na+/H+ exchange activity in mineralizing osteoblasts.
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High capacity Na+/H+ exchange activity in mineralizing osteoblasts.

机译：高容量Na + / H +交换活动矿化成骨细胞。

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摘要

Osteoblasts synthesize bone in polarized groups of cells sealed by tight junctions. Large amounts of acid are produced as bone mineral is precipitated. We addressed the mechanism by which cells manage this acid load by measuring intracellular pH (pHi) in non-transformed osteoblasts in response to weak acid or bicarbonate loading. Basal pHi in mineralizing osteoblasts was approximately 7.3 and decreased by approximately 1.4 units upon replacing extracellular Na(+) with N-methyl-D-glucamine. Loading with 40 mM acetic or propionic acids, in normal extracellular Na(+), caused only mild cytosolic acidification. In contrast, in Na(+) -free solutions, weak acids reduced pHi dramatically. After Na(+) reintroduction, pHi recovered rapidly, in keeping with Na(+) /H(+) exchanger (NHE) activity. Sodium-dependent pHi recovery from weak acid loading was inhibited by amiloride with the Ki consistent with NHEs. NHE1 and NHE6 were expressed strongly, and expression was upregulated highly, by mineralization, in human osteoblasts. Antibody labeling of mouse bone showed NHE1 on basolateral surfaces of all osteoblasts. NHE6 occurred on basolateral surfaces of osteoblasts mainly in areas of mineralization. Conversely, elevated HCO 3- alkalinized osteoblasts, and pH recovered in medium containing Cl(-), with or without Na(+), in keeping with Na(+) -independent Cl(-) /HCO 3- exchange. The exchanger AE2 also occurred on the basolateral surface of osteoblasts, consistent with Cl(-) /HCO 3- exchange for elimination of metabolic carbonate. Overexpression of NHE6 or knockdown of NHE1 in MG63 human osteosarcoma cells confirmed roles of NHE1 and NHE6 in maintaining pHi. We conclude that in mineralizing osteoblasts, slightly basic basal pHi is maintained, and external acid load is dissipated, by high-capacity Na(+) /H(+) exchange via NHE1 and NHE6.
机译：成骨细胞合成骨分化组细胞紧密连接的密封。酸生产骨矿物质沉淀。电池管理这种酸负载通过测量细胞内的pH值(φ)在非转换成骨细胞在弱酸或响应碳酸氢盐加载。成骨细胞是大约7.3,降低了大约1.4单位更换细胞外钠与N-methyl-D-glucamine(+)。装载和40毫米醋酸丙酸,正常细胞外钠(+),仅引起轻微胞质酸化。无解决方案,弱酸减少φ巨大的变化。迅速恢复,符合Na(+) /小时(+)换热器(新人道)活动。康复弱酸加载被抑制阿米洛利Ki nh一致。和NHE6表达强烈,表达被矿化调节高度,,在吗人类成骨细胞。骨显示NHE1管基底表面的造骨细胞。表面成骨细胞的主要地区矿化。碱化成骨细胞,pH值恢复中含Cl(-),有或没有Na (+),符合Na(+)独立Cl (-) / HCO 3 -交换。基底表面的成骨细胞,一致Cl (-) / HCO 3 -交换消除代谢碳酸盐。击倒的NHE1 MG63人类骨肉瘤细胞NHE1和NHE6确认角色维护φ。成骨细胞,略基础基底φ维护和外部酸负载消散,通过大容量钠(+)/小时(+)通过NHE1交换, and NHE6。

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