Perturbation of podocyte plasma membrane domains in experimental nephrosis. A lectin-binding and freeze-fracture study.

Alterations in the ultrastructural organization of podocyte plasma membrane domains were quantitatively assessed in puromycin aminonucleoside-treated rats by the use of 1) Helix pomatia lectin-gold complexes for detection of a specific glycocalyx component(s) normally associated with foot process bases and 2) freeze-fracture for detection of intramembrane particles and endocytotic invaginations on the plasma membrane. Lectin-binding sites were significantly reduced on podocyte foot process bases during the 7-day treatment period; and in freeze-fracture, the plasma membrane of the foot process base showed an increase in intramembrane particle number and size and an increased number of endocytotic invaginations, compared with the numbers in control animals. The cell body of nephrotic animals also had a significantly increased intramembrane particle density, compared with the control animals. These results provide direct evidence that the normal structure of specific plasma membrane regions is perturbed in podocytes that have lost their characteristic array of foot processes and support a role for these domains in the maintenance of normal podocyte architecture.