Proximal Tubule Sodium Handling in Calcium Stone Formers
It has been suggested that a high Na intake might be an etiological factor in idiopathic hypercalciuria (IH) and that in hypercalciuric Ca stone formers (CSF), Ca excretion (UCaV) can be normalized by reducing Na intake to less than 100 mEq/day without any change in Ca intake1. Moreover, in IH there might exist a proximal tubular “defect” in which there is reduced fractional reabsorption of Na, fluid, P, and possibly, Ca and Mg2,3. However, since the proximal tubule “defect” for Na is compensated at more distal sites of the tubule it cannot be the sole cause of the increased urinary Na excretion commonly seen in hypercalciuric patients1,3. We conclude that hypercalciuric patients must have an increased Na intake and have studied the relationship between Na intake, proximal tubular Na reabsorption and UCaV in healthy people and in a group of CSF to clarify the issue.
KeywordsIdiopathic Hypercalciuria Free Water Clearance Distal Delivery Fractional Delivery Fractional Reabsorption
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- 3.Y. K. Lau, H. Wasserstein, G. R. Westbey, P. Bosanac, M. Gabrie, P. Mitnick, E. Slatopolsky, S. Goldfarb, and Z. S. Agus, Min. Electrol. Metab. 7:237 (1982).Google Scholar