Lectin Cytochemistry of Cell Types in Human and Canine Pituitary

Labeled lectins specific for different sugars were employed to identify different cell types in pituitaries from six human autopsies and seven dogs. To determine the lectins bound by each cell type, fixed-paraffin embedded sections serial to those stained with lectins were immunostained for specific hormones and the serial pairs were examined in a comparison microscope. In human pituitaries corticotrophs stained selectively with lectins having affinity for alpha-L-fucose and the core region of complex type N-glycosyl-proteins. Some corticotrophs also stained for the presence of terminal beta-galactose. Thyrotrophs stained selectively with a periodate oxidation-borohydride reduction-concanavalin A sequence. Some mammotrophs evidenced content of glycoconjugate with terminal beta-galactose. Dendritic cells stained selectively for abundant glycogen with the periodate-reduction-concanavalin A sequence and a lectin from Griffonia simplicifolia. Adenohypophyseal cells of dog pituitary differed in showing absence of terminal beta-galactose in corticotrophs, presence of terminal beta-galactose in thyrotrophs, presence of glycoconjugate with N-glycosidically bound oligosaccharide in thyrotrophs and gonadotrophs and presence of terminal beta-galactose with a different lectin affinity in mammotrophs. The main contributions of lectin histochemistry applied to the pituitary include providing an additional histologic method for identification of some cell types, and localizing glycosylated prohormone or other biochemically unrecognized non-hormone glycoconjugates whose function in pituitary cells remains to be explained.