Morphological and functional aspects of the glomerular basement membrane.

Addition of Alcian Blue to the fixative reveals structural elements bearing negatively charged sites within the glomerular capillary wall of the rat kidney. According to previous research (review by Brenner et al., 1977), these charges represent one of the most important functional components of the glomerular filtration barrier. Alcian Blue also demonstrates negatively charged microfibrils (probably glycoproteins) of the mesangial matrix. Preliminary observations of glomeruli of lower vertebrates suggest that there is always a close correlation between the presence of microfibrils and mesangial cells.