QUANTITATION AND HISTOCHEMICAL-LOCALIZATION OF GALECTIN-1 AND GALECTIN-1-REACTIVE GLYCOCONJUGATES IN FETAL DEVELOPMENT OF BOVINE ORGANS

The display of cellular oligosaccharide chains is known to undergo mar ked developmental changes, as monitored histochemically with plant lec tins. In conjunction with endogenous lectins respective ligand structu res may have a functional role during fetal development. The assumptio n of a recognitive, functionally productive interplay prompts the stud y of the expression of a tissue lectin and of lectin-reactive glycocon jugates concomitantly. Focusing on common beta-galactosides as constit uents of oligosaccharide chains and the predominant member of the fami ly of galectins in mammals, namely galectin-1, the question therefore is addressed as to whether expression of lectin and lectin-reactive gl ycoconjugates exhibits alterations, assessed in three morphologically defined fetal stages and in adult bovine organs. Using a sandwich ELIS A, the level of the rather ubiquitous galectin-1 is mostly increased i n adult organs relative to respective fetal stages, except for the cas e of kidney. This developmental course is seen rather seldom, when the amounts of lectin-reactive glycoproteins or glycolipids are quantitat ed in solid-phase assays after tissue homogenization. Western blotting , combined with probing by labeled galectin-1, discloses primarily qua ntitative changes in the reactivity of individual glycoproteins. Perfo rming the same assays on extract aliquots with a plant agglutinin, nam ely the galactoside-binding mistletoe lectin, whose fine specificity i s different from galectin-1, its reduced extent of binding in solid-ph ase assays and the disparate profile of lectin-reactive glycoproteins reveal a non-uniform developmental alteration within the group of stru ctural variants of beta-galactosides. Although sample preparation can affect ligand preservation and/or presentation and thus restricts the comparability of biochemical and histochemical results, especially for soluble reactants, the histochemical studies on frozen and paraffin-e mbedded sections of bovine heart, kidney and liver demonstrate that th e localization of the galectin and of lectin-reactive epitopes can sho w a similar distribution, as seen in liver and heart, with organ-typic al quantitative changes of a rather similar staining profile (heart, k idney) or notable changes in the spatial distribution (liver) in the c ourse of development. This report emphasizes the potential value of co mbined monitoring of the lectin and its potential in vivo ligands to c ontribute to eventually unravel organ-related function(s) of a tissue lectin.