GLOMERULAR MESANGIUM ANALYSIS OF THE INCREASED ACTIVITY OBSERVED IN EXPERIMENTAL ACUTE AMINONUCLEOSIDE NEPHROSIS IN THE RAT

  • 1 January 1981
    • journal article
    • research article
    • Vol. 45  (5) , 400-409
Abstract
Kinetic studies have revealed increased mesangial macromolecular uptake in acute aminonucleoside of puromycin (PAN) nephrosis in the rat. The mechanisms leading to this increased activity are poorly understood. Mesangial function and ultrastructure were studied in rats 8 days after i.v. injection of 6 mg of PAN/100 g of body weight. No difference in mesangial C could be detected between PAN rats and controls 1 h after i.v. injection of 20 mg of colloidal C/100 g. After 24 h the amount of mesangial C was significantly higher in PAN rats; rates of disappearance did not differ. Ultrastructural examination revealed no differences in localization of mesangial C at the 1-h interval. After 24 h mesangial cells of PAN rats showed an increased number of lysosomes filled with C; the number of C particles in the mesangial matrix was not increased. Using an ultrastructural immunoperoxidase technique, increased amounts of endogenous IgG were found in the extracellular space of segmental mesangial lobules of PAN rats. IgG was mainly present in matrix substance of electron-lucent aspect, and quantitative morphometric analysis revealed an increase in volume of this loose permeable matrix component (mesangial channels). No increased staining of IgG was found in the lacis area indicating that there was no increased mesangial egress of macromolecules in PAN nephrosis. The increased volume of the permeable mesangial channels in segmental mesangial lobules of PAN rats may lead to a pooling of tracer material with consequent increased phagocytosis by mesangial cells.