Uptake and ultrastructural localization of a (125I) growth hormone releasing factor agonist in male rat pituitary gland: Evidence for internalization

Journal Article · Sun Sep 01 04:00:00 EDT 1991 · Endocrinology; (United States)

DOI:https://doi.org/10.1210/endo-129-3-1497· OSTI ID:5163037

Morel, G ^[1]

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1. CNRS URA 1454, Department of Histology, Lyon I University, Lyon-Sud Medical School, Oullins (France)

GRF was isolated from a human tumor of the pancreas and characterized. GRF stimulates the in vivo and in vitro secretion of GH. The present study was designed to find out whether human (h) GRF agonist could be internalized and to determine the subcellular localization of internalized peptide in somatotrophs. Autoradiography was performed on rat anterior pituitary glands removed at specific time intervals (2-60 min) after iv injection of monoradioiodinated (125I) (His1,Nle27) hGRF (1-32) NH2. Administration of an excess of unlabeled hGRF agonist along with the radioiodinated hormone prevented the uptake, indicating the specificity of the reaction. At the ultrastructural level only the somatotrophs appeared to contain silver grains. The main effect of hGRF agonist injection on the cytological aspect of the somatotrophs was a decrease in the area occupied by secretory granules, accompanied inversely, by an increase in that of the Golgi complex. The time course study in somatotrophs showed that five compartments (plasma membrane, secretory granules, cytoplasmic matrix, nuclear membrane, and lysosomes) have distinct marked labeling patterns. Plasma membrane, secretory granules, and nuclear membrane were labeled throughout the time course studied (2-60 min after injection). Cytoplasmic matrix was labeled 5 min post injection and lysosomes 15 and 30 min after injection. The Golgi complex, mitochondria, rough endoplasmic reticulum, and nucleus matrix were not labeled. The findings show the cellular specificity of GRF uptake by somatotrophs and the internalization process from the plasma membrane to the intracellular organelles (secretory granules, lysosomes, and nuclear membrane). Labeling of the secretory granule compartment suggests that granules may bind and protect internalized peptide from lysosomal degradation.

• OSTI ID: 5163037
• Journal Information: Endocrinology; (United States), Journal Name: Endocrinology; (United States) Vol. 129:3; ISSN ENDOA; ISSN 0013-7227
• Country of Publication: United States
• Language: English

Related Subjects

550201* -- Biochemistry-- Tracer Techniques
59 BASIC BIOLOGICAL SCIENCES
ANIMALS
AUTORADIOGRAPHY
BETA DECAY RADIOISOTOPES
BIOLOGICAL LOCALIZATION
BODY
CELL CONSTITUENTS
CELL MEMBRANES
CHEMICAL COMPOSITION
DAYS LIVING RADIOISOTOPES
DISTRIBUTION
ELECTRON CAPTURE RADIOISOTOPES
ENDOCRINE GLANDS
GLANDS
HORMONES
INTERMEDIATE MASS NUCLEI
INTERNAL CONVERSION RADIOISOTOPES
IODINE 125
IODINE ISOTOPES
ISOTOPE APPLICATIONS
ISOTOPES
MAMMALS
MAN
MEMBRANE TRANSPORT
MEMBRANES
MITOCHONDRIA
NUCLEI
ODD-EVEN NUCLEI
ORGANIC COMPOUNDS
ORGANS
PEPTIDE HORMONES
PITUITARY GLAND
PITUITARY HORMONES
PRIMATES
PROTEINS
RADIOISOTOPES
RATS
RODENTS
STH
SUBCELLULAR DISTRIBUTION
TRACER TECHNIQUES
VERTEBRATES