Ultrastructural autoradiographic localization of somatostatin-28 in the rat pituitary gland

Journal Article · Mon Apr 01 04:00:00 EST 1985 · Endocrinology; (United States)

DOI:https://doi.org/10.1210/endo-116-4-1615· OSTI ID:5480809

Morel, G; Leroux, P; Pelletier, G

To identify the anterior pituitary cell type(s) containing somatostatin-28 (SS-28)-binding sites and to study the internalization processes of this peptide by the target cells, autoradiography was performed on rat anterior pituitaries removed at specific intervals (2-60 min) after iv injection of the (/sup 125/I)iodo-SS-28 agonist (Leu8,D-Trp22,Tyr25)SS-28 into intact, adrenalectomized, or castrated male rats. At the light microscopic level, the silver grains were found in 75% of cells. Concomitant injection of an excess of unlabeled peptide prevented the binding of label, verifying the specificity of binding. No specific labeling could be detected in the adrenocorticotrophs of adrenalectomized rats or gonadotrophs (castration cells) of castrated rats. At the electron microscopic level, three cell types (somatotrophs, thyrotrophs, and mammotrophs) appear to contain radiolabeled SS-28. The time-course study in somatotrophs of intact animals showed that 2 min after injection, most silver grains were associated with the plasma membrane. Five to 15 min after injection, label was found over both the plasma membrane and cytoplasmic organelles, especially the Golgi apparatus, lysosomes, and secretory granules. At the longest time interval (60 min), labeling was mostly associated with the cytoplasmic organelles. These results indicate that SS-28-binding sites are present only in those cell types in which somatostatin is known to regulate secretory functions. The present data also show that a rapid internalization of the radiolabeled peptide occurs.

• Research Organization: Le Centre Hospitalier de l'Universite Laval, Quebec, Canada
• OSTI ID: 5480809
• Journal Information: Endocrinology; (United States), Journal Name: Endocrinology; (United States) Vol. 116:4; ISSN ENDOA
• Country of Publication: United States
• Language: English

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59 BASIC BIOLOGICAL SCIENCES
ADRENALECTOMY
ANIMALS
AUTORADIOGRAPHY
BETA DECAY RADIOISOTOPES
BODY
CASTRATION
CELL CONSTITUENTS
DAYS LIVING RADIOISOTOPES
DISTRIBUTION
ELECTRON CAPTURE RADIOISOTOPES
ELECTRON MICROSCOPY
ENDOCRINE GLANDS
GLANDS
INTERMEDIATE MASS NUCLEI
IODINE 125
IODINE ISOTOPES
ISOTOPES
LYSOSOMES
MAMMALS
MEDICINE
MICROSCOPY
NUCLEI
ODD-EVEN NUCLEI
ORGANOIDS
ORGANS
PITUITARY GLAND
RADIOISOTOPES
RATS
RECEPTORS
RODENTS
SOMATOSTATIN
SURGERY
TISSUE DISTRIBUTION
VERTEBRATES