Kulaksizoğlu Sevsen, Sofikerim Mustafa, Cevik Cemal
Department of Biochemistry, Faculty of Medicine, Başkent University, Konya, Turkey.
Int Urol Nephrol. 2008;40(3):589-94. doi: 10.1007/s11255-007-9256-0. Epub 2007 Aug 25.
In recent years significant progress has been made in identifying and quantitating physico-chemical processes involved in urinary stone formation. The ability of urine to inhibit calcium oxalate crystallization is an important mechanism against stone formation. Dietary factors appear to affect the ability of urine to inhibit calcium oxalate crystallization. These factors encouraged us to study the effects of lemon and orange juices on calcium oxalate crystallization in vitro.
The nucleation and aggregation of calcium oxalate monohydrate crystals were studied using turbidimetric 30-min time course measurements of optic density at 620 nm after mixing solutions containing calcium chloride and sodium oxalate at 37 degrees C, pH 5.7. The formation of crystals is induced by the addition of the oxalate and calcium solution. The effects on calcium oxalate crystal growth of trisodium citrate, lemon and orange juices were examined. The effects of lemon and orange juices were evaluated by the addition of 50 ml of juices. The optical density is measured at physiological conditions. The maximum increase of optic density with time, termed SN, reflects maximum rate of formation of new particles. After an equilibrium has been reached, a progressive decrease of optic density with time is observed. Rate of aggregation, SA, is derived from the maximum decrease in optic density.
Among the modifiers studied, citrate decreased both SN and SA (P<0.001). Lemon juice was also found to inhibit the rate of crystal nucleation and aggregation. But orange juice did not have any effect on the calcium oxalate crystallization (P>0.05).
These results show that effective prevention of urinary stone formation should aim at restoring the urine's ability to inhibit calcium oxalate crystallization and more emphasis should be given to dietary measures.
近年来，在识别和定量分析尿路结石形成过程中涉及的物理化学过程方面取得了重大进展。尿液抑制草酸钙结晶的能力是预防结石形成的重要机制。饮食因素似乎会影响尿液抑制草酸钙结晶的能力。这些因素促使我们研究柠檬汁和橙汁对草酸钙结晶的体外影响。
在37℃、pH 5.7条件下，将氯化钙溶液和草酸钠溶液混合后，采用比浊法在620nm波长下测量30分钟内的吸光度随时间变化过程，研究一水合草酸钙晶体的成核和聚集情况。通过添加草酸盐和钙溶液诱导晶体形成。考察了柠檬酸钠、柠檬汁和橙汁对草酸钙晶体生长的影响。通过添加50ml果汁来评估柠檬汁和橙汁的作用。在生理条件下测量吸光度。吸光度随时间的最大增加量，称为SN，反映了新颗粒形成的最大速率。达到平衡后，观察到吸光度随时间逐渐降低。聚集速率SA由吸光度的最大降低值得出。
在所研究的调节剂中，柠檬酸盐降低了SN和SA（P<0.001）。还发现柠檬汁能抑制晶体的成核和聚集速率。但橙汁对草酸钙结晶没有任何影响（P>0.05）。
这些结果表明，有效预防尿路结石形成应旨在恢复尿液抑制草酸钙结晶的能力，并且应更加重视饮食措施。
