Glycoconjugate localization with lectin and PA‐TCH‐SP cytochemistry in rat hypophysis

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Abstract
Glycoconjugates were localized by light microscopy with lectin‐peroxidase conjugates and by electron microscopy with the periodic acid‐thiocarbohydrazide‐silver proteinate (PA‐TCH‐SP) sequence in immunocyto‐chemically or morphologically identified cell types in rat pituitary. Lectin histochemistry demonstrated sialic acid and glycoconjugates with N‐glycosidically linked oligosaccharides in gonadotrophs, thyrotrophs, and corticotrophs. Galactose penultimate to sialic acid was observed mostly in gonadotrophs. The terminal galactose‐N‐acetylgalactosamine disaccharide was detected in a few gonadotrophs and in a moderate number of mammotrophs. Fucose was localized in only corticotrophs with two fucose‐binding lectins and in thyrotrophs with another. Several different monosaccharides were seen in glycoconjugates in melanotrophs and in Herring bodies. Melanotrophs displayed heterogeneous staining with fucose‐binding lectins. A small number of nonsecretory cells were also visualized in the pars distalis by virtue of their glycogen content. PA‐TCH‐SP staining revealed complex carbohydrates in secretory granules and some Golgi cisternae in all types of hormone‐producing cells in the pars distalis except for the somatotrophs. Melanotrophs of pars intermedia exhibited stained secretory granules and irregular dense bodies containing a stained meshwork. Corticotrophs of the pars distalis lacked the latter bodies, although they from the same glycoprotein precursor hormone as melanotrophs. Lectin conjugates and the PA‐TCH‐SP sequence stained some groups of secretion granules in Herring bodies, possibly representing vasopressin‐containing granules as well as other cell types in the pars nervosa.

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