The effects of different kinds of potassium carboxylates on the phase compositions of calcium oxalate (CaOxa) crystals grown in lecithin-water liposomes were first reported. The investigated potassium carboxylates included: monocarboxylate potassium acetate ( KAc), dicarboxylate potassium tartrate ( K_2tart) , tricarboxylate potassium citrate (K_3cit), and tetracarboxylate dipotassium of ethylenediaminetetraacetic acid (K_2edta). KAc only induces calcium oxalate monohydrate (COM) . Calcium oxalate trihydrate (COT) was induced when concentrations of K_2tart > 1.0 mmol/L. K_3cit and K_2edta can induce COM, calcium oxalate dihydrate (COD) and COT crystals depending on their concentrations. In a lower concentration range (1.0 ~ 17 mmol/L) , the COM content decreased and the COD content increased with increasing concentration of the K_3cit or K_2edta in logarithmic fashion. In a medium concentration range (3.3 to 17 mmol/L), only COD was grown. In a higher concentration range ( > 17 mmol/L) , COT was nucleated. The ability to induce COD follows the order: K_3cit > K_2edta > > K_2tart ~ KAc, and the ability to induce COT follows: K_2tart > > K3_cit > K_2edta > > KAc. Since the affinity of calcium oxalate hydrates to the membranes of renal tubule cells follows: COM > COT > COD, that is, COD is easily expelled from human body along with urine. So the inhibitory efficiency of potassium carboxylates on CaOxa stones can be deduced as K_3cit > K_2edta > > K_2tart > > KAc.

Key words: calcium oxalate, liposome, potassium carboxylate, biomineralization, urinary stone, CRYSTAL GROWTH