Lectin binding on carbohydrate compounds of the flask cells in the claw-frog kidney

The carbohydrate compounds of the mucus of flask cells in the kidney of claw-frogs (Xenopus laevis) were analysed through lectin binding studies. After removing epoxy resin semithin sections were incubated with 7 lectins (WGA, RCA I, PNA, LCH, UEA, LPA) marked by horseradish peroxidase and 2 unmarked lectins (VAA, Con A). The glycosaminoglycans in the canalicular lumen of flask cells showed a strong reaction with WGA and RCA, whereas the binding of PHA, Con A, and LCH was weaker. No reaction was observed with PNA, UEA, LPA, and VAA. The mucus of the flask cells seems to be rich in N-acetyl-glycosamine and -galactosamine. It contains also mannose, glucose, and galactose, but seems to have no fucose or N-acetyl-sialic acid residues.