Stabilization of calcium oxalate suspension by urinary macromolecules, probably an efficient protection from stone formation.
BACKGROUND
Crystal aggregation (AGN) destabilizes crystal suspensions and during crystalluria probably favors crystal apposition to kidney calcifications and preexisting stones. We analyzed inhibition of AGN and stabilization of calcium oxalate suspensions by urinary macromolecules (UM), urine and solutions with urinary citrate concentration.


METHODS
Solutions of UM (UMS) were obtained by a hemofiltration procedure from urine of 6 healthy men. Calcium oxalate suspensions were prepared in all solutions and urine by adjusting Ca2+ to 1.5 mM and by an oxalate titration to 1.0 mM. Crystallization was monitored measuring optical density (OD). Stability of suspensions (SS) was defined as the time without sedimentation and zeta potential (ZP) of crystals was measured. AGN was visualized by scanning electron microscopy and quantified by maximal OD.


RESULTS
UMS inhibited AGN and increased ZP and SS. Most inhibitory activity of urine could be attributed to UM. 3.3-fold dilution of UM reduced SS only by 30%.


CONCLUSIONS
During crystalluria, UM of healthy men are supposed to protect from stone formation by inhibiting AGN and stabilizing crystal suspensions. As a probably important aspect, this protection was found to be limited in time and may favorably be influenced by an increase of diuresis.
Baumann
J M
JM
Stone Research Center Viollier, Biel, Switzerland.
Affolter
B
B
Caprez
U
U
Clivaz
C
C
Glück
Z
Z
Weber
R
R
D002129:Calcium Oxalate / Q000737:chemistry / Q000652:urine*; D002951:Citrates / Q000737:chemistry; D003460:Crystallization; D006440:Hemofiltration; D006801:Humans; D046911:Macromolecular Substances / Q000652:urine*; D008297:Male; D008855:Microscopy, Electron, Scanning; D013499:Surface Properties; D013997:Time Factors; D052878:Urolithiasis / Q000517:prevention & control* / Q000652:urine
D002951:Citrates; D046911:Macromolecular Substances; D002129:Calcium Oxalate