Characterization and regulation of somatostatin receptors in rat pituitary cells

Thesis/Dissertation · Tue Jan 01 04:00:00 EST 1985

OSTI ID:6898212

Presky, D H

This research investigated the interaction of the hypothalamic peptide somatostatin (SRIF) with GH/sub 4/C/sub 1/ rat pituitary tumor cells. Using an acid extraction technique to discriminate between intracellular and surface-bound peptide, the author found that neither receptor-bound (/sup 125/I-Tyr/sup 1/)SRIF nor (/sup 125/I-Tyr/sup 11/)SRIF was rapidly internalized. However, both radioanalogs were partially (50/70%) degraded to /sup 125/I-tyrosine prior to dissociation. Since the lysosomal inhibitors leupetin, ammonium chlorine and chloroquine did not reduce receptor mediated SRIF degradation, this process must be nonlysosomal. In contrast, epidermal growth factor (EGF) was rapidly internalized and degraded to /sup 125/I-tyrosine in lysosomes. Chronic treatment of cells with SRIF increased the number of SRIF receptors. This increase required 15 h to reach a plateau level of 220% of untreated controls and was dose-dependent (ED/sub 50/ = 2 nM). The effects of SRIF treatment on receptor modulation were specific for the SRIF receptor. Modulation of SRIF binding was not mimicked by other agents which regulate hormone release indicated that occupancy of SRIF receptors triggered this event. Detailed analysis of the binding kinetics of (/sup 125/I-Tyr/sup 11/)SRIF showed that this radioanalog was superior to (/sup 125/I-Tyr/sup 11/)SRIF for binding studies in cells due to its higher affinity for the SRIF receptor. Photo-affinity labelling and affinity cross-linking experiments identified the EGF receptor as a protein with a molecular weight of 180,000. The SRIF receptor, however, could not be identified with these techniques.

• Research Organization: Harvard Univ., Boston, MA (USA)
• OSTI ID: 6898212
• Country of Publication: United States
• Language: English

Related Subjects

550201 -- Biochemistry-- Tracer Techniques
550601* -- Medicine-- Unsealed Radionuclides in Diagnostics
59 BASIC BIOLOGICAL SCIENCES
62 RADIOLOGY AND NUCLEAR MEDICINE
AMINO ACIDS
ANIMALS
BETA DECAY RADIOISOTOPES
BIOCHEMICAL REACTION KINETICS
BODY
CARBOXYLIC ACIDS
CHEMICAL REACTIONS
CROSS-LINKING
DAYS LIVING RADIOISOTOPES
DOSE-RESPONSE RELATIONSHIPS
ELECTRON CAPTURE RADIOISOTOPES
ENDOCRINE GLANDS
GLANDS
HYDROXY ACIDS
INTERMEDIATE MASS NUCLEI
IODINE 125
IODINE ISOTOPES
ISOTOPE APPLICATIONS
ISOTOPES
KINETICS
MAMMALS
MEMBRANE PROTEINS
NUCLEI
ODD-EVEN NUCLEI
ORGANIC ACIDS
ORGANIC COMPOUNDS
ORGANS
PITUITARY GLAND
POLYMERIZATION
PROTEINS
RADIOISOTOPES
RADIORECEPTOR ASSAY
RATS
REACTION KINETICS
RECEPTORS
RODENTS
SOMATOSTATIN
TRACER TECHNIQUES
TYROSINE
VERTEBRATES