Stone matrix as proteins adsorbed on crystal surfaces: a microscopic study

Abstract

All urinary concretions are composed of a crystalline or mineral phase and a non-crystalline phase. Both phases vary markedly in their chemical nature. There are a number of theories about the role and morphogenesis of the organic phase or matrix. In our opinion, at least a part of the matrix is formed by adsorption of urinary proteins onto crystal surfaces. It has already been shown that naturally occurring polymers have an affinity for calcium oxalate crystal surfaces and that spaces filled with amorphous substances exist between calcium oxalate monohydrate crystals of whewellite renal stones. We wanted to visualize these crystal surfaces with adsorbed organic material. We studied calcium oxalate monohydrate crystals from urinary stones, and crystal made in a crystallizer and incubated in gamma globulin or bovine serum albumin. We also studied calcium oxalate monohydrate crystals experimentally induced in rat renal tubules. They were studied using light, scanning and transmission electron microscopy with, as well as without, EDTA digestion. All crystals were surrounded by an amorphous coat which may have originated by adsorption of proteins on crystal surfaces.