The isolation and partial characterization of rat kidney stone matrix induced by magnesium deficiency

Dietary magnesium deficiency in rats has been employed to generate kidney stones in a relatively short period of time. Stones have been observed in situ and examined histochemically. Techniques have been devised for the isolation of the kidney stones and for the demineralization of the stones. The gross morphological character of isolated concretions has been examined microscopically, and the mineral composition determined by X-ray emission analysis. Hydroxyapatite was found to be the mineral component. Decalcification and subsequent dialysis of stones revealed that about 60% of the stone, on a dry weight basis, consists of apatite, and about. 5.8% consists of a nondialyzable organic component termed matrix.

A variety of chemical analyses were done on this matrix material. These tests included elemental analysis, amino acid analysis, a variety of carbohydrate assays, fatty acid analysis, a cholesterol determination, phosphate analysis, and measurements of calcium and magnesium content. From these studies, about 60% of the matrix composition has been determined, the majority of which are amino acids and neutral carbohydrate.

The origin and function of kidney stone matrix are unknown. Possible answers to these questions have been presented, although insufficient data does not permit any conclusive statement to be made. Knowledge of.the composition of matrix may be useful in determining its origin.