Histochemical evaluation of application of biotinylated neoglycoproteins for the detection of endogenous sugar receptors in fish skin.

The physiological importance of recognitive protein-carbohydrate interactions is by no means restricted to mammals. Thus, the analysis of expression of sugar receptors in lower vertebrates is warranted, employing carrier-immobilized carbohydrate ligands. The present work initiates such a systematic glycohistochemical mapping of endogenous sugar receptor expression, focussing on fish epidermis. A battery of biotinylated neoglycoproteins exposing 11 different types of ligand structures, and the avidin-biotin-peroxidase complex (ABC) technique has been used to assess extent of binding on Bouin's solution-fixed paraffin-embedded specimens. The semi-quantitative evaluation disclosed both quantitative and qualitative site-associated differences in expression of endogenous lectins by the integument constituents. Moreover, a distinct expression of sugar receptors by two or three types of trunk myocytes was also observed. This study thus emphasized the feasibility of glycohistochemistry with neoglycoproteins, conducted in lower vertebrates. The approach used with carbohydrate constituents of cellular glycosubstances as ligands in search of specific receptors is proposed to be a powerful complementary tool in carbohydrate histochemistry to the monitoring of the carbohydrate structures by labelled plant or invertebrate lectins and a step to elucidate the functional significance of protein-carbohydrate interactions.