Chick embryo metanephros: the glycosylation pattern as revealed with lectin conjugates

Fragments of metanephros were taken from chick embryos and studied from the 7th to the 21st d of incubation. A battery of 7 different horseradish peroxidase-labelled lectins (PNA, ConA, DBA, SBA, LTA, WGA and UEA I) was used to analyse the distribution and changes of carbohydrate moieties in glycoconjugates along the metanephric nephron from the S-shaped body stage onwards. DBA and SBA reacted for a short time at some sites during the considered period of incubation. Provided WGA and ConA reacted with most of the nephric components, the almost ubiquitous presence of N-acetyl-D-glucosamine and alpha-D-mannose was demonstrated. SBA and LTA were found to be good markers of the proximal tubule. On the 12th d of incubation, sialic acid was found in the podocytes, capillary walls, and the connecting and collecting ducts. On the same day, other oligosaccharides were present at the nephric tubular components. The simultaneous presence of sialic acid and other sugar residues may be significant for the identification of the exact stage of incubation at which metanephric activity starts. The possible role of some sugar residues for the regulation of metanephric activity is discussed.