/sup 125/I and /sup 125/I-glucagon metabolism in rat liver
This report suggests that the time course and enzymatic nature of /sup 125/I-insulin degradation in vivo correlates with major subcellular locations of autoradiographic grains during the course of endocytosis. /sup 125/I-insulin and hormone fragments were detected in liver extracts using reverse-phase high performance liquid chromatography (RP-HPLC). /sup 125/I-insulin was rapidly degraded in vivo. Comparison with autoradiographic studies suggests insulin degradation begins before substantial lysosomal localization is observed. Studies using an isolated perfused rat liver system suggest that the plasmalemma does not mediate rapid insulin degradation as observed in vivo. The author, therefore, sought to identify /sup 125/I-insulin fragments which typified the activities of the most-implicated intracellular degradative systems: acidic lysosomal proteolysis, a microsomal reductive system such as glutathione-insulin transhydrogenase (GIT), and a cytosolic neutral proteolytic system such as insulin protease. Significant GIT activity was not observed in vivo nor in vitro with liver homogenates. Purified liver insulin protease degraded /sup 125/I-insulin in a fashion similar to that observed in vivo. Lysosomal activity was observed only after a lag of approximately 10 minutes. Complete degradation of /sup 125/I-glucagon in vivo occurred within 1 minute of hormone injection.
- Research Organization:
- Minnesota Univ., Minneapolis (USA)
- OSTI ID:
- 6067513
- Resource Relation:
- Other Information: Thesis (Ph. D.)
- Country of Publication:
- United States
- Language:
- English
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GLUCAGON
METABOLISM
HYDROGENASES
ENZYME ACTIVITY
INSULIN
PEPTIDE HYDROLASES
AUTORADIOGRAPHY
IODINE 125
LIQUID COLUMN CHROMATOGRAPHY
LIVER
LYSOSOMES
RATS
TRACER TECHNIQUES
ANIMALS
BETA DECAY RADIOISOTOPES
BODY
CELL CONSTITUENTS
CHROMATOGRAPHY
DAYS LIVING RADIOISOTOPES
DIGESTIVE SYSTEM
ELECTRON CAPTURE RADIOISOTOPES
ENZYMES
GLANDS
HORMONES
HYDROLASES
INTERMEDIATE MASS NUCLEI
IODINE ISOTOPES
ISOTOPE APPLICATIONS
ISOTOPES
MAMMALS
NUCLEI
ODD-EVEN NUCLEI
ORGANIC COMPOUNDS
ORGANOIDS
ORGANS
OXIDOREDUCTASES
PEPTIDE HORMONES
PEPTIDES
POLYPEPTIDES
PROTEINS
RADIOISOTOPES
RODENTS
SEPARATION PROCESSES
VERTEBRATES
550501* - Metabolism- Tracer Techniques