Processing of receptor-bound somatostatin: internalization and degradation by pancreatic acini
The authors have previously demonstrated the presence of specific binding sites for somatostatin on plasma membranes from pancreatic acinar cells. In the present study they attempted to characterize the fate of receptor-bound /sup 125/I-(Tyr/sup 11/)somatostatin. Internalization of somatostatin was rapid (reaching a plateau at 20% of the cell-associated specific radioactivity) and temperature dependent. To follow the processing of bound somatostatin, acini were incubated with /sup 125/I-(Tyr/sup 11/)somatostatin at 5/sup 0/C during 16 h then, after washing, incubated at 37/sup 0/C for 90 min in fresh medium. Surface-bound somatostatin decreased rapidly, whereas radioactivity increased in the cell interior and the incubation medium. Intracellular and membrane-bound radioactivity was mainly intact /sup 125/I-(Tyr/sup 11/)somatostatin. Degradation occurred at the plasma membrane level and led to iodotyrosine production. After 15 min of incubation, 15% of the initially surface-bound /sup 125/I-(Tyr/sup 11/)somatostatin was compartmentalized within the cell, mainly in the microsomal fraction. After 30 min, a significant increase in radioactivity appeared in the nuclear fraction. These results indicate that the major part of somatostatin cellular degradation takes place at the plasma membrane level. Within the cell, somatostatin is routed to the nucleus via particular fractions sedimenting with microsomal vesicles.
- Research Organization:
- Institut National de la Sante et de la Recherche Medicale, Toulouse, France
- OSTI ID:
- 5879285
- Journal Information:
- Am. J. Physiol.; (United States), Vol. 252:4
- Country of Publication:
- United States
- Language:
- English
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LABELLED COMPOUNDS
BIODEGRADATION
UPTAKE
SOMATOSTATIN
AMYLASE
CELL MEMBRANES
DOSE-RESPONSE RELATIONSHIPS
GUINEA PIGS
IODINE 125
LACTATE DEHYDROGENASE
PANCREAS
RECEPTORS
TYROSINE
AMINO ACIDS
ANIMALS
BETA DECAY RADIOISOTOPES
BODY
CARBOXYLIC ACIDS
CELL CONSTITUENTS
CHEMICAL REACTIONS
DAYS LIVING RADIOISOTOPES
DECOMPOSITION
DIGESTIVE SYSTEM
ELECTRON CAPTURE RADIOISOTOPES
ENDOCRINE GLANDS
ENZYMES
GLANDS
GLYCOSYL HYDROLASES
HEMIACETAL DEHYDROGENASES
HYDROLASES
HYDROXY ACIDS
INTERMEDIATE MASS NUCLEI
IODINE ISOTOPES
ISOTOPES
MAMMALS
MEMBRANE PROTEINS
MEMBRANES
NUCLEI
O-GLYCOSYL HYDROLASES
ODD-EVEN NUCLEI
ORGANIC ACIDS
ORGANIC COMPOUNDS
ORGANS
OXIDOREDUCTASES
PROTEINS
RADIOISOTOPES
RODENTS
VERTEBRATES
550201* - Biochemistry- Tracer Techniques