Analysis of the Protein Content of Five Different Types of Kidney Stones

Abstract

The aim of this study was to characterize the protein matrix of five different types1 of kidney stones: calcium oxalate monohydrate (type I), calcium oxalate dihydrate (type II), uric acid (type III), struvite (type IV) and cystine (type V). After extraction of calcium salts, the proteins were run on sodium dodecyl sulphate polyacrylamide gel electrophoresis (SDS-PAGE) and analyzed by Western blot experiments using specific antibodies. In all types, the most abundant protein found was albumin (HSA). α-l-acid glycoprotein, α-1-microglobulin, immunoglobulins A, G, M (Igs A, G, M), apolipoprotein Al, transferrin and α-1-antitrypsin were also present in the five types of calculi. β-2-microglobulin was only found in types I, II and HI. Furthermore, using antibodies to pancreatic lithostathine, an inhibitor of CaCO3 crystal growth in pancreatic juice, we were able to detect an immunologically related protein in all types of stones (figure 1). Conversely, we failed to detect caeruloplasmin, haptoglobulin and, surprisingly, the Tamm-Horsfall protein (THP) which is the most abundant protein in normal urine.