**Author details**

**6. Summary and conclusions**

174 Pathophysiology - Altered Physiological States

coats or is mediated by self-aggregated but normal UMs.

The formation of Ca stones in the kidney during crystalluria seems to base on crystal AGN either on Randall's plugs or on plaques. Urine has, as demonstrated by our study, a high inhibitor capacity with respect to CaOx AGN. Coating of crystals by electronegative charged UMs creates zones of electrostatic repulsion between the crystals which under normal conditions and within the short urinary transit time in the kidney hardly can be overwhelmed by diffusion or sedimentation being responsible for particle collision and thus AGN. Zones of electrostatic repulsion are reduced in the presence of pathological UMs with a lack of anionic residues or in concentrated urine with a high ionic strength. UMs with a lack of negatively charged anionic groups create an insufficient surface potential on UM-coated crystals. At high ionic strength, the extent of surface potentials is compressed by an increased accumulation of cations. Under these conditions, zones of electrostatic repulsion probably can be bridged by normal but self-aggregated UMs. Self-AGN occurs by the adsorption of UMs on surfaces especially of HAP with its high affinity to UMs. The AGN of UM-coated particles like urinary crystals or latex beads probably mainly bases on a hydrophobic effect between the large hydrophobic protein segments. This effect can occur either directly between pathological UM

**Figure 9.** Almost identical results obtained in crystallization test (CT) performed with concentrated urine (•) and albumin solution (AS, 20 mg/l (o): CT performed in native urine or AS (native), in urine or AS with UM or albumin

coated HAP (+cHAP) and in dissolved Ca phosphate precipitates of urine or AS (DP) (*n* = 8, *x* ± SD).

Stone formation on Randall's plugs mainly occurs at high urinary supersaturation with respect to Ca salts as observed in primary hyperoxaluria or in hyperparathyroidism both with Johannes M. Baumann

Address all correspondence to: johannes.denise.baumann@bluewin.ch

Stone Research Center Biel, Biel, Switzerland
