To better understand urinary inhibitors of calcium oxalate crystallization, both zeta potential measurement and particle size analysis were chosen to illustrate: (1) the potential therapeutic efficacy of G872, a semi-synthetic sulfated polysaccharide, in stone prevention; and (2) the relative contribution of various urinary fractions {e.g., ultrafiltered urine (UFU), Tamm-Horsfall protein (THP), urinary polyanionsprecipitated with cetylpyridinium chloride (CPC), urinary macromolecular substances with different concentration ratios (UMSl0,50,90 and UMS\u27l0,50,90) and THP-free urine (THPFU)} to total urinary inhibitory activity. The results showed: (1) addition of G872 significantly enhances urinary inhibitory activity and negative zeta potential values; (2) re-addition of the CPC to UFU completely restores urinary inhibitory activity; and (3) artificial urines prepared by mixing UMS\u27 10,50,90 from THPFU with UFU differed in inhibitory activity from that prepared by mixing UMSl0,50,90 from a pooled normal urine with UFU. Based on these experimental results, the following speculations can be made: (1) normal human urines are considered to be a protective colloidal system; (2) urinary inhibitory activity originates mainly from CPC and/or UMS; (3) normal THP is a protective material to maintain urinary inhibitory activity; and (4) mutual interaction between urinary inhibitors may change the total urinary inhibitory activity
