The objective of this study was to evaluate the hypothesis that a high concentration of ionized calcium in the lumen of the medullary collecting duct causes an osmole-free water diuresis. The urine flow rate and osmolality were measured in normal human subjects, as well as in patients with a history of nephrolithiasis who excreted more than 5 mmol of calcium per 24 h. There was an inverse relationship between the concentration of calcium in the urine and the 24 h urine volume both in normal subjects and in patients with a history of nephrolithiasis. When the concentration of calcium in the urine was greater than 5 mmol/l, the urine volume was less than 1 litre per day in the majority of subjects. After 16 h of water deprivation, when the concentration of calcium in the urine was as high as 17 mmol/l (ionized calcium 7.4 mmol/l), urine osmolality was 1258 mOsm/kg of water and the urine flow rate was 0.30 ml/min. We conclude that, although a calcium receptor may be present in the lumen of the medullary collecting duct in human subjects, an extremely high concentration of urinary total and ionized calcium does not cause a clinically important defect in the renal concentrating process.
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Research Article|
February 09 2000
Does a high concentration of calcium in the urine cause an important renal concentrating defect in human subjects?
George S. S. LAM;
George S. S. LAM
*Renal Division, St. Michael's Hospital, University of Toronto, Toronto, Ontario M5B 1A6, Canada
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John R. ASPLIN;
John R. ASPLIN
†Renal Division, University of Chicago, Chicago, IL 60637, U.S.A.
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Mitchell L. HALPERIN
*Renal Division, St. Michael's Hospital, University of Toronto, Toronto, Ontario M5B 1A6, Canada
Correspondence: Professor M. L. Halperin, Professor of Medicine, St. Michael's Hospital Annex, Lab g1, Research Wing, 38 Shuter Street, Toronto, Ontario M5B 1A6, Canada (e-mail [email protected]).
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Publisher: Portland Press Ltd
Received:
August 06 1999
Revision Received:
November 01 1999
Accepted:
December 06 1999
Online ISSN: 1470-8736
Print ISSN: 0143-5221
The Biochemical Society and the Medical Research Society © 2000
2000
Clin Sci (Lond) (2000) 98 (3): 313–319.
Article history
Received:
August 06 1999
Revision Received:
November 01 1999
Accepted:
December 06 1999
Citation
George S. S. LAM, John R. ASPLIN, Mitchell L. HALPERIN; Does a high concentration of calcium in the urine cause an important renal concentrating defect in human subjects?. Clin Sci (Lond) 1 March 2000; 98 (3): 313–319. doi: https://doi.org/10.1042/cs0980313
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