Calcium Oxalate and Calcium Phosphate Crystal Formation and Inhibition in Agarose Gel System

Lee, Eun Sik; Lee, Chong Wook

Abstract

An in vitro method using agarose gel which is chemically stable and easily soluble for growing various stones is developed. The optimal conditions for formation of stone crystals in agarose gel were defined as 0.75% of gel concentration, 7ml of gel volume and 24mm of diameter of test tube. We studied the formation and inhibition of calcium oxalate and calcium phosphate crystals which comprises most urinary stones. Calcium containing stones formed under different conditions including pH in this media were identified by qualitative and quantitative analysis and light as well as scanning electron microscopic examination. Calcium oxalate monohydrate(whewellite) was formed in all pH condition, calcium hydro genphosphate dehydrate(brushite) in pH 5.5 and octacalcium phosphate in pH 7.5. The results obtained indicate that agarose gel system is a good model for an investigation of stone crystal formation because of its simplicity and reproducibility. The effects of known inhibitor, magnesium, citrate and pyrophosphate to the formation of calcium oxalate and calcium phosphate crystals were explored in this system. The inhibitory activity of pyrophosphate was maximum, then citrate, magnesium in order, in both calcium oxalate monohydrate and octacalcium phosphate crystal formation and the activity was not influenced by a variation in pH. However the activity of these inhibitors was minimal in calcium hydrogenphosphate dehydrate. According to the findings that the appearance of the crystal was similar, but size of it was smaller in the formed crystals which was under influence of the inhibitors, the inhibitory activity appeared to exerted on the process of crystal aggregation.