CALCIUM-OXALATE LITHOGENESIS - INFLUENCE OF URINE FROM NON-LITHIASIC SUBJECTS ON CRYSTALLIZATION

In the present study we aim at describing the influence of urine of no n-lithiasic subjects on the different crystallization stages of calciu m oxalates. The experimental method consists in comparing the turbidim etric curves obtained by crystallization in pure synthetic urine to th e curves obtained after addition of natural urine to the solution. Nat ural urine plays an important role on nucleation, crystal growth and a gglomeration even if only small amounts (4% v/v) are added to the moth er solution. Nucleation is favoured (decrease of the induction period and increase of the crystal number) by the presence of solid particule s, such as cellular fragments, which play the role of substrates for h eterogeneous nucleation. On the other hand, both the growth rate of th e crystals and their degree of agglomeration are reduced. Moreover, th e physical nature of the crystals which precipitate is different from that of the crystals which nucleate in synthetic urine. Under our cond itions of high supersaturation, natural urine favours the nucleation o f calcium oxalate dihydrate at the expenses of calcium oxalate trihydr ate which forms in pure synthetic urine. A hypothesis on the origin of the lithogenesis process is made and a correlation between the locali zation of the calcium oxalate stones in the urinary tracts and their m ain constituents is proposed.