Ultrastructural distribution of glomerular basement membrane components in experimental diabetes

To investigate possible changes in the organization of the constitutive elements of the glomerular basement membrane during diabetes we have localized type IV collagen, entactin, laminin and heparan sulfate proteoglycan on the glomerular wall of control and long-term streptozotocin-induced diabetic animals. To do so, we made use of specific polyclonal antibodies and the high resolution protein A-gold immunocytochemical technique. The morphometrical analysis of the labelling has demonstrated that each antigen displays a specific distribution in the glomerular basement membrane of normal animals. In diabetes, changes in type IV collagen were detected with an accentuation of the labelling on the endothelial side and the presence of a wider region weakly labelled on the epithelial side of the basement membrane. No differences were found in the distribution of other components in normal and diabetic conditions, beside a decrease in the labelling for heparan sulfate proteoglycan in the laminae rarae. These modifications may influence the interactions among the various basement membrane components which in turn, will affect the structural organization of the polymeric matrix of the basement membrane, leading to a loss in selective permeability.