Ultrastructural localization of sulphate glycoconjugates in the human glomerular capillary wall using the high iron diamine method

: The distribution of fixed anionic sites within glomerular capillary walls has been studied in man by applying two ultrastructural histochemical methods--the high iron diamine and dialysed colloidal iron methods--to tissue chopper sections and to isolated glomeruli obtained from surgical fragments of renal tissue. By using the high iron diamine method we have been able to demonstrate that in man, too, there are sulphate (possibly heparan sulphate proteoglycan) sites preferentially located in the lamina rara esterna of the basement membrane and in the cell coat of the urinary surface of podocytes. Non-sulphate (high iron diamine-negative, dialysed colloidal iron-positive) anionic sites have been identified not only in the glycocalyx of the epithelial and endothelial cells but also in the laminae rarae of the basement membranes, where they show a more extensive distribution pattern than sulphate sites. The proposed methods seem particularly suitable for the study of human renal tissue; they could, in fact, provide useful information about the behaviour of the various anionic components of the glomerular capillary wall in pathological conditions.