Asplin J R, Mandel N S, Coe F L
Nephrology Section, University of Chicago, Illinois 60637, USA.
Am J Physiol. 1996 Apr;270(4 Pt 2):F604-13. doi: 10.1152/ajprenal.1996.270.4.F604.
We have used published rat micropuncture data to construct a matrix of ion concentrations along the rat nephron. With an iterative computer model of known ion interactions, we calculated relative supersaturation ratios in all nephron segments. The collecting ducts and urine showed expected supersaturation with stone-forming salts. Fluid in the thin segment of the loop of Henle may be supersaturated with calcium carbonate and calcium phosphate under certain conditions. Because calculations cannot predict the actual course of crystallization, we made solutions to mimic, in vitro, presumed conditions in the loop of Henle. The solid phases that formed were analyzed by X-ray powder diffraction, electron microprobe, and infrared spectroscopy. All samples were identified as poorly crystallized or immature apatite. The descending limb of Henle's loop creates a unique condition as it extracts water but not sodium, bicarbonate, calcium, or phosphate, giving a calcium concentration at the bend of 3 mM, pH 7.4, and a phosphate concentration that varies from 0.8 to 48 mM, depending on parathyroid hormone and dietary phosphate. We conclude that conditions in the thin segment potentially could create a solid calcium phosphate phase, which may initiate nucleation of calcium oxalate salts in the collecting ducts, potentiating nephrolithiasis and nephrocalcinosis.
我们利用已发表的大鼠微穿刺数据构建了沿大鼠肾单位的离子浓度矩阵。借助已知离子相互作用的迭代计算机模型，我们计算了所有肾单位节段中的相对过饱和率。集合管和尿液中呈现出与结石形成盐类预期的过饱和情况。在某些条件下，亨氏袢细段中的液体可能会出现碳酸钙和磷酸钙过饱和。由于计算无法预测结晶的实际过程，我们制备了溶液，在体外模拟亨氏袢中的假定条件。通过X射线粉末衍射、电子微探针和红外光谱对形成的固相进行了分析。所有样品均被鉴定为结晶不良或不成熟的磷灰石。亨氏袢降支营造了一种独特的条件，因为它重吸收水分但不重吸收钠、碳酸氢根、钙或磷酸盐，在袢的弯曲处钙浓度为3 mM，pH值为7.4，磷酸盐浓度则根据甲状旁腺激素和饮食中的磷酸盐含量在0.8至48 mM之间变化。我们得出结论，细段中的条件可能会形成磷酸钙固相，这可能会引发集合管中草酸钙盐的成核，从而加剧肾结石和肾钙质沉着症。
