Saso L, Valentini G, Leone M G, Grippa E, Silvestrini B
Institute of Pharmacology and Pharmacognosy, University of Rome 'La Sapienza', Rome, Italy.
Urol Int. 1998;61(4):210-4. doi: 10.1159/000030331.
Despite the risk of kidney damage, lithotripsy is the usual way of treating calcium oxalate (CaOx) stones, the most common type of nephrolithiasis, because no effective chemolytic agents are available. However, the search of new calcium chelators, less toxic than the current ones, continues, and some of them could be tested in experimental models of nephrolithiasis, after their ability of dissolving CaOx crystals is verified. In this connection, we developed a simple assay that requires only inexpensive equipment available in most laboratories for the screening of substances potentially capable of dissolving CaOx crystals. In particular, we decided to investigate whether substances previously shown to inhibit CaOx precipitation were also capable of dissolving this salt. Briefly, CaOx tablets of highly reproducible weight (4.55 +/- 0.07 mg) were prepared by spinning, at high speed (16,000 g), microcentrifuge tubes in which 500 microl aliquots of 0.1 M sodium oxalate and 0.1 M calcium chloride at pH 6 were added. When these tablets were incubated overnight with solutions at different concentrations of EDTA, sodium citrate, manganese chloride, sodium sulfate, sodium chloride, malic acid, succinic acid and gluconic acid, a significant dissolving activity was observed for EDTA ( approximately 25% at 0.25 M), sodium citrate ( approximately 30% at 1 M) and manganese chloride ( approximately 20% at 0.5 M). A good linear correlation (r2 = 0.84, p < 0.05) was found between the affinity for calcium and the activity of EDTA, sodium citrate, sodium sulfate, malic acid, succinic acid and gluconic acid, indicating that these compounds act mainly by chelating the calcium ion. Instead, manganese was supposed to act by interacting with the oxalate ion.
尽管存在肾损伤风险，但由于没有有效的化学溶解剂，体外冲击波碎石术仍是治疗草酸钙（CaOx）结石（最常见的肾结石类型）的常用方法。然而，人们仍在继续寻找毒性低于现有药物的新型钙螯合剂，其中一些在其溶解CaOx晶体的能力得到验证后，可在肾结石实验模型中进行测试。在此方面，我们开发了一种简单的检测方法，该方法仅需要大多数实验室都具备的廉价设备，用于筛选可能能够溶解CaOx晶体的物质。特别是，我们决定研究先前显示可抑制CaOx沉淀的物质是否也能够溶解这种盐。简而言之，通过高速（16,000 g）旋转微量离心管来制备重量高度可重复（4.55 +/- 0.07 mg）的CaOx片剂，其中加入了500微升pH为6的0.1 M草酸钠和0.1 M氯化钙。当这些片剂与不同浓度的EDTA、柠檬酸钠、氯化锰、硫酸钠、氯化钠、苹果酸、琥珀酸和葡萄糖酸溶液一起孵育过夜时，观察到EDTA（0.25 M时约为25%）、柠檬酸钠（1 M时约为30%）和氯化锰（0.5 M时约为20%）具有显著的溶解活性。发现钙亲和力与EDTA、柠檬酸钠、硫酸钠、苹果酸、琥珀酸和葡萄糖酸的活性之间存在良好的线性相关性（r2 = 0.84，p < 0.05），表明这些化合物主要通过螯合钙离子起作用。相反，锰被认为是通过与草酸根离子相互作用起作用。
