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Quantitative studies of human urinary excretion of uropontin.
Kidney Int. 1998 Jan; 53(1):189-93.KI

Abstract

Uropontin is the urinary form of osteopontin, an aspartic acid-rich phosphorylated glycoprotein. Uropontin has been previously shown to be a potent inhibitor of the nucleation, growth and aggregation of calcium oxalate crystals and the binding of these crystals to renal epithelial cells. Quantitative data defining the excretion of this protein are necessary to determine its role in urinary stone formation. In the present studies, we determined uropontin excretion rates of normal humans. Urine samples were obtained under conditions of known dietary intake from young adult human volunteers with no history, radiographic or laboratory evidence of renal disease. Urinary concentrations of uropontin were measured by a sensitive ELISA employing an affinity purified polyclonal antiserum to uropontin. Thirteen normal subjects ingested a constant diet providing 1 gram of calcium, 1 gram of phosphorus, 150 mEq of sodium and 1 gram of protein per kilogram of body wt per day during an eight day study period. The relationship of urinary volume to uropontin excretion was assessed by varying fluid intake on the last four days of the study to change the mean urine volume/24 hr by > 500 ml. Urine collected in six hour aliquots for eight days was analyzed for uropontin by ELISA, and for calcium, and creatinine. Daily uropontin excretion of 13 individual subjects was 3805 +/- 1805 micrograms/24 hr (mean +/- 1 SD). The mean urinary levels (1.9 micrograms/ml) detected in the present study are sufficient for inhibition of crystallization; our previous studies have demonstrated that the nucleation, growth and aggregation of calcium oxalate crystals and their binding to renal cells in vitro are inhibited by this concentration of purified uropontin. In contrast to the regular pattern of diurnal variation of calcium excretion seen in most subjects, uropontin excretion showed no regularity of diurnal variation and was not directly related to either calcium or creatinine excretion or changes in urinary volume. However, uropontin concentration varied inversely with urine volume (P < or = 0.001), so that the highest uropontin concentrations occurred when urine volume was the lowest. We conclude that the physiologic characteristic of an inverse relationship of uropontin concentration to urine volume favors protection from urinary crystallization of calcium oxalate by uropontin. Our quantitative definition of urinary uropontin excretion of normal adults provides the basis for the evaluation of uropontin excretion by individuals who have formed urinary stones.

Authors+Show Affiliations

Department of Pediatrics, University of Pennsylvania, Philadelphia, USA.No affiliation info availableNo affiliation info availableNo affiliation info availableNo affiliation info availableNo affiliation info available

Pub Type(s)

Journal Article
Research Support, Non-U.S. Gov't
Research Support, U.S. Gov't, P.H.S.

Language

eng

PubMed ID

9453017

Citation

Min, W, et al. "Quantitative Studies of Human Urinary Excretion of Uropontin." Kidney International, vol. 53, no. 1, 1998, pp. 189-93.
Min W, Shiraga H, Chalko C, et al. Quantitative studies of human urinary excretion of uropontin. Kidney Int. 1998;53(1):189-93.
Min, W., Shiraga, H., Chalko, C., Goldfarb, S., Krishna, G. G., & Hoyer, J. R. (1998). Quantitative studies of human urinary excretion of uropontin. Kidney International, 53(1), 189-93.
Min W, et al. Quantitative Studies of Human Urinary Excretion of Uropontin. Kidney Int. 1998;53(1):189-93. PubMed PMID: 9453017.
* Article titles in AMA citation format should be in sentence-case
TY - JOUR T1 - Quantitative studies of human urinary excretion of uropontin. AU - Min,W, AU - Shiraga,H, AU - Chalko,C, AU - Goldfarb,S, AU - Krishna,G G, AU - Hoyer,J R, PY - 1998/2/7/pubmed PY - 1998/2/7/medline PY - 1998/2/7/entrez SP - 189 EP - 93 JF - Kidney international JO - Kidney Int VL - 53 IS - 1 N2 - Uropontin is the urinary form of osteopontin, an aspartic acid-rich phosphorylated glycoprotein. Uropontin has been previously shown to be a potent inhibitor of the nucleation, growth and aggregation of calcium oxalate crystals and the binding of these crystals to renal epithelial cells. Quantitative data defining the excretion of this protein are necessary to determine its role in urinary stone formation. In the present studies, we determined uropontin excretion rates of normal humans. Urine samples were obtained under conditions of known dietary intake from young adult human volunteers with no history, radiographic or laboratory evidence of renal disease. Urinary concentrations of uropontin were measured by a sensitive ELISA employing an affinity purified polyclonal antiserum to uropontin. Thirteen normal subjects ingested a constant diet providing 1 gram of calcium, 1 gram of phosphorus, 150 mEq of sodium and 1 gram of protein per kilogram of body wt per day during an eight day study period. The relationship of urinary volume to uropontin excretion was assessed by varying fluid intake on the last four days of the study to change the mean urine volume/24 hr by > 500 ml. Urine collected in six hour aliquots for eight days was analyzed for uropontin by ELISA, and for calcium, and creatinine. Daily uropontin excretion of 13 individual subjects was 3805 +/- 1805 micrograms/24 hr (mean +/- 1 SD). The mean urinary levels (1.9 micrograms/ml) detected in the present study are sufficient for inhibition of crystallization; our previous studies have demonstrated that the nucleation, growth and aggregation of calcium oxalate crystals and their binding to renal cells in vitro are inhibited by this concentration of purified uropontin. In contrast to the regular pattern of diurnal variation of calcium excretion seen in most subjects, uropontin excretion showed no regularity of diurnal variation and was not directly related to either calcium or creatinine excretion or changes in urinary volume. However, uropontin concentration varied inversely with urine volume (P < or = 0.001), so that the highest uropontin concentrations occurred when urine volume was the lowest. We conclude that the physiologic characteristic of an inverse relationship of uropontin concentration to urine volume favors protection from urinary crystallization of calcium oxalate by uropontin. Our quantitative definition of urinary uropontin excretion of normal adults provides the basis for the evaluation of uropontin excretion by individuals who have formed urinary stones. SN - 0085-2538 UR - https://www.unboundmedicine.com/medline/citation/9453017/Quantitative_studies_of_human_urinary_excretion_of_uropontin_ L2 - https://linkinghub.elsevier.com/retrieve/pii/S0085-2538(15)60380-5 DB - PRIME DP - Unbound Medicine ER -