Replacement of hydroxylapatite by whewellite: implications for kidney-stone formation
Replacement of hydroxylapatite by whewellite: implications for kidney-stone formation
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DOI：
10.1180/minmag.2014.078.1.07
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发表时间：
2014-02
影响因子：
2.7
通讯作者：
I. Sethmann;B. Grohe;H. Kleebe
中科院分区：
文献类型：
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作者：
I. Sethmann;B. Grohe;H. Kleebe
摘要肾结石主要由一水草酸钙（COM）组成，常被发现附着在肾软组织中形成的羟基磷灰石（HA）斑块上，导致病变并暴露于尿液。虽然结石形成的过程还不完全清楚，但公认的观点是，所谓的兰德尔斑块作为COM晶体成核和从相应的过饱和尿液中生长的基质。然而，这里提出的结果表明，一个额外的矿物替代过程。在实验方法中，HA在0.25 mM、0.5 mM和1.0 mM草酸盐溶液中反应，pH范围为4.5至7.5，模拟尿液中遇到的正常至苛刻条件。极酸性溶液诱导HA晶体溶解，再加上释放的Ca 2+离子作为COM在HA表面上再沉淀。相反，当骨被用作基质时，更类似于病理性斑块（有机基质内聚集的HA纳米晶体），即使在温和得多的流体条件下（通常在尿液中发现），也会诱导HA-COM矿物质置换反应。因此，COM部分取代和结壳兰德尔斑块的过程可能发生在特发性结石形成者的尿路中，代表肾结石的潜在起始事件。
Abstract Kidney stones consisting predominantly of whewellite (calcium oxalate monohydrate, COM) are often found attached to hydroxylapatite (HA) plaques that form in the soft tissue of kidneys, cause lesions and become exposed to urine. Although the processes of stone formation are not entirely known, it is an established view that so-called Randall’s plaques serve as substrates for COM crystal nucleation and growth from correspondingly supersaturated urine. However, the results presented here suggest an additional mineral replacement process is involved. In an experimental approach, HA was reacted in 0.25 mM, 0.5 mM and 1.0 mM oxalate solutions with pH ranging from 4.5 to 7.5, simulating normal to harsh conditions encountered in urine. Extremely acidic solutions induce dissolution of HA crystals coupled with re-precipitation of the released Ca2+ ions as COM on the HA surface. When, instead, bone was used as a substrate, being more similar to the pathological plaque (aggregated HA nanocrystals within an organic matrix), the HA-COM mineral-replacement reaction is induced even under much milder fluid conditions, commonly found in urine. Hence, a process of COM partly replacing and encrusting Randall’s plaque may take place in the urinary tract of idiopathic stone formers, representing a potential starting event for nephrolithiasis.