Urinary stone formation is a common human disease accounting for about 1% of hospital admissions in the United States. It is estimated that in the US alone, treatment of the stone related disorders cost at least 2.4 billion dollars/year. Recurrence rate is up to 60% and one third of the patients with recurrent kidney stones may lose the involved kidney. Seventy to eighty percent of the stones contain calcium oxalate (CaOx). Initial event in urinary stone formation is crystal nucleation which is determined to be heterogeneous. Cellular degradation products and membrane bound vesicles are common in mammalian urine and calcific urinary stones. Membrane bound vesicles can induce nucleation which is determined to be phosphate (CaP) and CaOx in vitro. Both CaP and CaOx crystals produced in rat kidneys are almost always formed in association with the membranous vesicles. Based on these observations nucleation of calcific crystals in urine is proposed to be mediated by cellular membranes and their lipids. All vesicles may however not be endowed with the capabilities to nucleate crystals. Apparently there are specific domains on membrane surfaces and only the vesicles with those domains can induce crystal nucleation. What are those domains? How do they become available to the contents of the renal tubular fluid or urine? Goals of this project are to find answers to these and related questions and to develop an understanding of the mechanisms involved in membrane associated crystallization of calcium containing crystals. CaOx crystalluria and nephrolithiasis will be induced in male Sprague-Dawley rats. Lipids associated with the urinary and renal crystal events will be isolated and identified to determine any specificity. CaOx crystal formation will be induced in vitro by incubation of membrane vesicles in a metastable solution of CaOx. Crystal associated vesicles will be separated from the non-crystal associated vesicles by density gradient centrifugation. Lipids of both types of vesicles will be isolated and identified. To investigate actions of various phospholipids, Langmuir monolayers containing specific lipid combinations will be made and their role in nucleation and growth of CaOx crystals will be examined.

Agency
National Institute of Health (NIH)
Institute
National Institute of Diabetes and Digestive and Kidney Diseases (NIDDK)
Type
Research Project (R01)
Project #
5R01DK041434-08
Application #
2734079
Study Section
Special Emphasis Panel (ZRG4-GRM (02))
Project Start
1991-01-01
Project End
2000-06-30
Budget Start
1998-07-05
Budget End
1999-06-30
Support Year
8
Fiscal Year
1998
Total Cost
Indirect Cost
Name
University of Florida
Department
Pathology
Type
Schools of Medicine
DUNS #
073130411
City
Gainesville
State
FL
Country
United States
Zip Code
32611
Khan, Saeed R (2002) Stone research on the bench: where we are and where we are going. J Endourol 16:413-6
Khan, Saeed R; Glenton, Patricia A; Backov, Renal et al. (2002) Presence of lipids in urine, crystals and stones: implications for the formation of kidney stones. Kidney Int 62:2062-72
Fasano, J M; Khan, S R (2001) Intratubular crystallization of calcium oxalate in the presence of membrane vesicles: an in vitro study. Kidney Int 59:169-78
Gokhale, J A; Glenton, P A; Khan, S R (2001) Characterization of Tamm-Horsfall protein in a rat nephrolithiasis model. J Urol 166:1492-7
Moriyama, M T; Glenton, P A; Khan, S R (2001) Expression of inter-alpha inhibitor related proteins in kidneys and urine of hyperoxaluric rats. J Urol 165:1687-92
Khan, S R; Maslamani, S A; Atmani, F et al. (2000) Membranes and their constituents as promoters of calcium oxalate crystal formation in human urine. Calcif Tissue Int 66:90-6
Khan, S R; Thamilselvan, S (2000) Nephrolithiasis: a consequence of renal epithelial cell exposure to oxalate and calcium oxalate crystals. Mol Urol 4:305-12
Thamilselvan, S; Byer, K J; Hackett, R L et al. (2000) Free radical scavengers, catalase and superoxide dismutase provide protection from oxalate-associated injury to LLC-PK1 and MDCK cells. J Urol 164:224-9
Maslamani, S; Glenton, P A; Khan, S R (2000) Changes in urine macromolecular composition during processing. J Urol 164:230-6
Thamilselvan, S; Hackett, R L; Khan, S R (1999) Cells of proximal and distal tubular origin respond differently to challenges of oxalate and calcium oxalate crystals. J Am Soc Nephrol 10 Suppl 14:S452-6

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