Distribution of heterologous antiperoxidase antibodies and their fragments in the superficial renal cortex of normal Wistar-Munich rat: an ultrastructural study.

The distribution of serum proteins in the superficial renal cortex of normal Wistar-Munich rats was studied using a new technique. Heterologous antiperoxidase antibodies (160,000 daltons), their F(ab')2(100,000 daltons), and Fab (50,000 daltons) fragments were injected intravenously and then demonstrated by incubation with free peroxidase after in situ fixation. This technique offered several advantages including easy and uniform detection of the proteins, even in tubular cells, and a high degree of specificity and accuracy. Four findings emerged from this: (1) The glomerular filtration barrier was found to be complete for IgG and incomplete for (ab')2 and Fab fragments. (2) This barrier for IgG was localized in the lamina densa. (3) The filtered proteins were found to be reabsorbed and degraded in the proximal tubule. (4) The three proteins were diffusely detected in the interstitial tissue and in tubular intercellular spaces up to apical tight junctions.