LIGHT-MICROSCOPIC AND ELECTRON-MICROSCOPIC IMMUNOCYTOCHEMISTRY OF SOMATOTROPES IN THE ANTERIOR-PITUITARY GLAND OF EUROPEAN FERRET, MUSTELA-PUTORIUS-FURO

Light-microscopic immunocytochemistry of ferret anterior pituitary rev ealed the localization of somatotropes in the pars distalis, but no im munoreactive cells were detected in the pars tuberalis. Ultrastructura l studies by superimposition immunocytochemistry and immuno-electron m icroscopy, elucidated the morphological heterogeneity of these somatot ropic cells. They were classified into 2 subtypes on the basis of size of the secretory granules. Type-I cells with small granules (mean dia meter, 192 nm), were considered to be the immature somatotrop, while T ype-II cells, with comparatively larger secretory granules (mean diame ter, 257 nm), were considered to be the matured form of Type-I cells a nd the typical somatotropic cell-type, and were much more predominant than the Type-I cells. The fact that Type-II cells had a distinct Golg i zone and many mitochondria, while in Type-I cells the intracellular organelles were generally less developed, supports this suggestion In addition to these two extreme subtypes, several intermediate forms wer e also encountered that may represent different transitional phases du ring the conversion of Type I to Type II. Protein A-gold immuno-electr on microscopy illustrated the specific localization of growth hormone over the granules, with no labelling over any other cytoplasmic organe lles of the 2 somatotrope subtypes.