Lectin-binding sites during postnatal differentiation of normal and cystic rabbit renal corpuscles.

Abstract

Fluorochrome-labeled lectins were used to study the expression of glycoconjugates during the postnatal differentiation of normal and cystic rabbit renal corpuscles. Glomerular cysts (GC) are induced in the rabbit by a single injection of corticoids. The Bowman's capsule of these cysts is exclusively formed of podocytes (parietal podocytes). During normal development, the cell coat of the podocytes is intensely positive for wheat germ agglutinin (WGA) and Maclura pomifera agglutinin (MPA). This reaction decreases considerably during maturation, in parallel with an increase in the number of binding sites masked by terminal sialylation. Throughout the stages studied, the podocyte coat is peanut agglutinin (PNA)-negative, but it becomes intensely positive after neuraminidase treatment. Visceral and parietal podocytes in the glomerular cysts show the same pattern of glycosylation as the normal podocytes. In contrast, normal parietal cells only transiently expressed a weak reactivity to WGA and MPA during the first stages of differentiation, and did not express cryptic binding sites at any stage. The glomerular basement membrane (GBM) is positive to WGA, to succinylated WGA, and to MPA, in all the stages studied. Maturation of the GBM is characterized by expression of cryptic MPA-binding sites, and by a considerable increase in the number of cryptic PNA-binding sites. The basement membrane of the parietal layer of the cystic Bowman's capsule shows the same pattern of glycosylation, despite the fact that this epithelial layer is solely formed of podocytes and lacks endothelial cells. In contrast, the normal parietal basement membrane does not express PNA or MPA cryptic sites at any stage.(ABSTRACT TRUNCATED AT 250 WORDS)