Crystal attachment to injured renal collecting duct cells: influence of urine proteins and pH.
BACKGROUND
The attachment of crystals to injured kidney epithelium is thought to be a necessary event in the development of urolithiasis. In vivo, the crystals are coated with urinary macromolecules that define the surface properties of the crystals. The present study examines the influence of coating of calcium oxalate crystals with urinary macromolecules on their attachment to both healthy (polarized) and injured (nonpolarized) primary inner medullary collecting duct (IMCD) cells.


METHODS
Calcium oxalate monohydrate (COM) and calcium oxalate dihydrate (COD) crystals were coated with urine macromolecules by incubating the crystals in urine from normal healthy volunteers at pH 5, 6, and 7. The level of attachment of the coated crystals to IMCD cells was also determined at pH 5, 6, and 7. The adsorbed proteins were extracted from the crystal surfaces and separated by gel electrophoresis.


RESULTS
The coating of calcium oxalate crystals with urine proteins greatly reduced the attachment of crystals to both control and injured IMCD cells. At pH levels below 6, the crystals readily attached to injured cells. Extraction and separation of the adsorbed proteins showed that both COM and COD crystals adsorbed a similar array of proteins. At pH 5 and 6, several trace proteins were adsorbed to the crystals and were not apparent at pH 7.


CONCLUSIONS
The coating of crystals with urine macromolecules greatly reduces the attachment of the crystals to normal healthy epithelia. The coating and attachment of the crystals below pH 6 enhances the attachment to injured cells. The enhanced crystal attachment could possibly be associated with one or more proteins adsorbed to the crystal surface that are not adsorbed to the crystals at higher pH.
Wiessner
John H
JH
Department of Medicine, Medical College of Wisconsin and Department of Veterans Affairs Medical Center, Milwaukee, Wisconsin 53295, USA. wiessner@mcw.edu
Hung
Linda Y
LY
Mandel
Neil S
NS
D000818:Animals; D002129:Calcium Oxalate / Q000737:chemistry / Q000652:urine; D002478:Cells, Cultured; D003460:Crystallization; D006863:Hydrogen-Ion Concentration; D007685:Kidney Tubules, Collecting / Q000737:chemistry* / Q000166:cytology; D051381:Rats; D014545:Urinary Calculi / Q000737:chemistry* / Q000209:etiology* / Q000652:urine; D014556:Urine / Q000737:chemistry*
D002129:Calcium Oxalate