in calculogenesis of urinary stones

and other, semisynthetic, sulphated polysaccharides are thought o play an important role in urolithiasis. Processes involved in urinary stone formation are crystallization and crystal retention. Oxalate transport and renal tubular cell injury are determining factors in these processes. In this article experimental results concerning the possible mech-anisms of action of GAGs and other sulphated polysac-charides are reviewed. GAGs are inhibitors of crystal growth and agglomeration and possibly also of nucle-ation. They can prevent crystal adherence, correct an ab-normal oxalate flux and prevent renal tubular cell dam-age. Sulphated polysaccharides can be divided in two sub-groups, namely, glycosaminoglycans (GAGs) and other semi-synthetic sulphated polysaccharides. GAGs are poly-anionic polysaccharide chains composed of repeating di-saccharides of identical composition and variable lengths. Their molecular weight varies between 2 × 103 and 3 x 106 Da. All have a similar structure with one of the five prin-cipal polymers hyaluronate, chondroitin, keratan, derma-tan or heparan. All except hyaluronic acid may be cova-lently attached to protein as proteoglycans [35]. GAGs are widely distributed in the body. Many physi-ological functions are attributed to these substances, but little is known in detail about their synthesis, distribution and metabolism. In adults, approximately 250 mg GAG is produced each day, only 10 % of which is excreted in the urine. Urinary GAGs are enzymatic degradation products of proteoglycans that are excreted by glomerular filtration [50]. Renal tubular secretion or reabsorption has not been demonstrated [37]. Their excretion shows a circadian rhythm. Men excrete significantly more GAGs per 24 h than women, the levels varying between 10 and 30 gmol/ day as based upon measurements of the glucuronic acid moiety. Normal urine contains about 2 % GAGs. Of th