ABSTRACT
Crystallization and deposition of calcium salts are common phenomena (1). Generally the processes are physiologically necessary for the well being of the individual. But occasionally they are abnormal and pathological with devastating consequences causing a wide variety of diseases and disorders including urinary stones, dental calculus, salivary stones, biliary stones, crystal deposition in joints, various forms of ectopic calcification, and failure of catheters and bioprosthetic devices (2). While calcium phosphate deposition can be either physiological or pathological, calcium oxalate deposition is typically pathological. In spite of these differences, a number of similarities exist between the normal and abnormal crystallization processes; for example, both types of crystallization require existence of supersaturation, occur in the presence of nucleating substrates and are influenced positively as well as negatively by a variety of modulators. In addition, all products of crystallization are comprised of a crystalline phase and a non-crystalline phase, usually called matrix. A consensus is developing that both types of crystallization mechanisms involve cellular membranes, specifically their phospholipids which play an important initiating role (3). Using the example of urinary stones we will discuss here the role of membranes in crystallization of calcium phosphate (CaP) and calcium oxalate (CaOx).
