Calcium Oxalate Crystal Aggregation Research Articles

Glycosaminoglycans as inhibitors of calcium oxalate crystal growth and aggregation

Evidence is presented that the glycosaminoglycans, chondroitin 6-sulphate and chondroitin 4-sulphate, are the major inhibitors of calcium oxalate crystal growth and aggregation in dilute normal urine.

Studies on Some Possible Biochemical Treatments of Primary Hyperoxaluria

The effects of some putative inhibitors of oxalate production or urinary oxalate excretion have been investigated in the Cynamolgus monkey and in patients with Type I primary hyperoxaluria (hyperoxaluria with glycollic aciduria). Sodium-1-hydroxybutan-sulphonate, D,L-phenyllactate, succinimide and isocarboxazide did not reduce the urinary oxalate excretion in the monkeys. Pyridoxine reduced the excretion of oxalate and glycollate in some patients, and its therapeutic use has been documented over a five-year period. Succinimide, which has been used by other workers for the treatment of non-hyperoxaluric stone formers, did not decrease the excretion of either oxalate or glycollate in three patients in whom it was tried. It did not change the inhibitory activity of the urine with respect to the growth and aggregation of calcium oxalate crystals in any of the three patients, and it did not have any consistent effect on the excretion of calcium oxalate crystals in the one patient who had detectable crystaluria before treatment. We have identified several metabolites of succinimide in the urine of patients taking the drug. These include 2,3-dehydrosuccinamic, 2-hydroxysuccinamic and 3-hydroxysuccinamic acids. Isocarboxazide, cholestyramine and thiamine did not affect the urinary oxalate excretion in the patients. The significance of these observations from the viewpoint of the treatment of primary hyperoxaluria is discussed.

Aggregation of calcium oxalate crystals: effect of urine and various inhibitors.

The influence of various factors on aggregation of calcium oxalate crystals in vitro was determined. Aggregation was assessed by filtering the crystal suspension and measuring the flow rate through a filter. 10% urine completely inhibited aggregation. Orthophosphate and magnesium at concentrations occuring in urine had no effect. Citrate had no effect at 10(-4) M ,but did inhibit at 10(-3) M. The latter effect is probably due to calcium binding. Pyrophosphate and disodium dichioromethylene diphosphonate (C12MDP) inhibited strongly at 10(-4) M, disodium ethane-1-hydroxy-1,1-diphosphonate (EHDP) at 10(-5) M, whereas pentanemonophosphonate had no effect. Uromucoid also did not show any inhibitory activity. Studies by means of heat inactivation, ultrafiltration and fractionation on DEAE-cellulose and gel-filtration indicated that the inhibitory activity was heterogenous and that the major part was larger than 10 000 daltons.

The effect of ethane-1-hydroxy-1,1-diphosphonate (EHDP) on calcium oxalate crystalluria in recurrent renal stoneformers.

1. The volume, size and type of calcium oxalate crystals excreted in the urine of a group of patients with recurrent ‘idiopathic’ stones were studied on a controlled basal diet, after an oral supplement of sodium oxalate and after oral administration of ethane-1-hydroxy-1,1-diphosphonate (EHDP) for 4 weeks. 2. Before administration of EHDP the stone-formers passed the large crystals and aggregates of calcium oxalate dihydrate characteristic of recurrent calcium oxalate stone-formers. For the same level of urine saturation and crystalluria EHDP caused a significant reduction in the proportion of large crystals and aggregates excreted. Studies by light-microscopy confirmed that EHDP caused a striking change in the size and habit of calcium oxalate crystals in some but not all of the urine samples examined. 3. The decrease in average crystal size during the administration of EHDP was attributed to the observed increase in the ability of urine to inhibit the growth and aggregation of calcium oxalate crystals as measured by a growth system in vitro. 4. The possible use of EHDP as a therapeutic agent in the treatment of calcium oxalate stone-formation is discussed.

Inhibitors of the growth and aggregation of calcium oxalate crystals in vitro

A sensitive method has been developed for measuring the effect of inhibitors of crystallisation on the growth and aggregation of calcium oxalate crystals in vitro. Of the known inhibitors tested the highly charged anions pyrophosphate and ethane-1-hydroxy-1,1-diphosphonate (EHDP) were effective down to concentrations of 0.1–1 μmole/l and the polyanions heparin and chondroitin sulphate A down to concentrations of 1 nmole/l. Within the normal range of urea concentrations found in urine the neutral molecule urea caused a small but significant degree of inhibition. At higher concentrations the degree of inhibition increased sharply. In the concentrations tested the cations magnesium and methylene blue had no effect on the growth and aggregation of crystals. These findings suggest that highly charged anions and polyanions may have some clinical value as a possible treatment for recurrent calcium oxalate stone-formation in man.

Calcium oxalate crystalluria and inhibitors of crystallization in recurrent renal stone-formers.

1. The particle size distributions of calcium oxalate crystals were measured at 37°C in fresh urine from recurrent, idiopathic stone-formers and their controls under the same conditions of dietary and fluid intake. The crystals excreted by the controls were small and belonged to a unimodal distribution, whereas those excreted by the stone-formers belonged to a distribution which contained a second peak of much larger particles. The proportion of large crystals in the urines of the stone-formers was significantly higher than in the urines of the controls. 2. The difference in the proportion of large particles passed by the two groups was accentuated by adding a small quantity of sodium oxalate to their diets. Whereas the controls continued to excrete only small crystals of calcium oxalate, the stone-formers passed most of their crystals as large particles. 3. Further investigations showed that the urines of the controls contained a potent inhibitor of the growth and aggregation of calcium oxalate crystals in vitro and that the inhibitor was deficient in the urines of the recurrent stone-formers. 4. It is suggested that the inhibitor in normal urine may allow calcium oxalate to be passed harmlessly in the form of small particles, whereas the lower inhibitory activity in the urines of the recurrent stone-formers is insufficient to prevent the growth of the primary crystals into the large aggregates seen in these urines. By blocking the formation of abnormally large crystals and aggregates the inhibitor may therefore play an important role in preventing crystalluria leading to stone formation.