CALCIUM-OXALATE INTERACTION IN MODULATION OF STONE FORMATION

这个子项目是利用由NIH/NCRR资助的中心拨款提供的资源的许多研究子项目之一。子项目和调查员(PI)可能从另一个NIH来源获得了主要资金，因此可能会出现在其他CRISE条目中。列出的机构是针对中心的，而不一定是针对调查员的机构。这个项目解决了最近引起相当大兴趣的一个话题，涉及到饮食限制钙要么无效，要么可能夸大结石形成的可能性。这一担忧的基础是在肠道和尿液中发生的所谓的钙-草酸相互作用。我们是最早描述肠道草酸-钙相互作用的人之一，也就是说，由于肠道中的钙与草酸结合，导致尿中草酸排泄的变化。在低钙摄入期间，没有足够的鲁米诺钙来结合草酸，增加草酸吸收和尿草酸。在急性胰腺炎中，尿草酸可能轻度-中度升高，因为肠道对钙的吸收增加，导致钙不足以与草酸结合。高钙摄入量有望消除或减缓尿草酸的升高。限制因素是饮食中的草酸含量，因为鲁米那钙与饮食中的草酸相结合。这一部分旨在阐明“钙-草酸相互作用”，即钙通过结合肠道中的草酸影响尿液中总草酸的量，以及通过络合草酸影响尿液中离子草酸的量。通过这一过程，限钙可以增加尿草酸，减缓尿草酸钙饱和度的下降，这可能是由于尿钙下降所致。相反，高钙摄入量可能会降低尿液中的总草酸和离子草酸，与尿钙增加可能导致的尿草酸钙饱和度升高相反。需要检验的总体假设是，钙-草酸相互作用取决于饮食草酸限制、肠道对钙的吸收状态或高钙尿症的程度，以及钙是作为食物还是作为补充剂提供的。这一部分的目标是完成检验上述假设所需的其余研究。

This subproject is one of many research subprojects utilizing the resources provided by a Center grant funded by NIH/NCRR. The subproject and investigator (PI) may have received primary funding from another NIH source, and thus could be represented in other CRISP entries. The institution listed is for the Center, which is not necessarily the institution for the investigator. This project addresses a topic that has raised considerable interest recently, dealing with the possibility that dietary calcium restriction is either ineffective or may exaggerate stone formation. The basis for this concern is the so-called calcium-oxalate interaction that occurs in the bowel and in urine. We were among the first to describe oxalate-calcium interaction in the bowel, i.e., changes in urinary oxalate excretion from binding of oxalate by calcium in the intestinal tract. During low calcium intake, there is inadequate luminal calcium to bind oxalate, increasing oxalate absorption and urinary oxalate. In AH, urinary oxalate may be mild-moderately increased, because increased intestinal absorption of calcium leaves insufficient amount of calcium to bind oxalate. A high calcium intake would be expected to eliminate or attenuate the rise in urinary oxalate. The limiting factor is dietary oxalate content, since it is dietary oxalate that is bound by luminal calcium. This component is directed at elucidating the "calcium-oxalate interaction", a process by which calcium affects the amount of total oxalate in urine by binding oxalate in the intestinal tract, as well as the amount of ionic oxalate in urine by complexing oxalate. By this process, calcium restriction could increase urinary oxalate, attenuating the decline in urinary saturation of calcium oxalate that might ensue from the fall in urinary calcium. Conversely, a high calcium intake could lower total and ionic oxalate in urine, opposing the rise in urinary saturation of calcium oxalate that might occur from increased urinary calcium. The overall hypothesis to be tested is that calcium-oxalate interaction is dependent on dietary oxalate restriction, the state of intestinal absorption of calcium or the degree of hypercalciuria, and on whether calcium is provided as food or supplement. The objective of this component is to complete remaining studies required to test the above hypothesis.