VARIATIONS IN THE SIALIC ACID CONCENTRATION OF GLOMERULAR BASEMENT MEMBRANE PREPARATIONS OBTAINED BY ULTRASONIC TREATMENT

Abstract

Several authors (10, 15, 6, 1, 20) have suggested that sialic acid is a component of the glomerular basement membrane (BM) . Investigations by Spiro (20) have shown that BM preparations obtained by ultrasonic treatment of whole glomeruli contain two distinct carbohydrate moieties, in approximately equal proportions : one is a disaccharide containing glucose and galactose, believed to be intrinsically associated with collagen, and the other is a heteropolysaccharide consisting of galactose, mannose, hexosamines, sialic acid, and fucose . We have presented histochemical evidence that sialic acid is present in the glomerulus and that it is located not in the basement membrane proper but in the cell membranes lining the basement membrane (18, 14). Preceding us, Rambourg and Leblond (17) demonstrated a carbohydrate-rich cell coat, acidic in nature, at the surface of glomerular cells, and recently Gronowski et al . (3) and Jones (4) published results similar to ours . The present study was undertaken in an attempt to demonstrate that basement membrane preparations obtained by ultrasonic treatment, a customary procedure for biochemical analysis, are contaminated by cell membranes and that the sialic acid content of such preparations increases with the rising centrifugal force at which they are collected .