Effect of concentration on hepatic transport of exogenous epidermal growth factor

Journal Article · Fri Mar 01 04:00:00 EST 1985 · Hepatology (N.Y.); (United States)

DOI:https://doi.org/10.1002/hep.1840050209· OSTI ID:5411222

Burwen, S J; Barker, M E; Goldman, I S; Jones, A L

Epidermal growth factor (EGF), taken up by rat hepatocytes, is primarily transported to the lysosomes and degraded. However, a small but significant percentage of endocytosed EGF is transported by a nonlysosomal pathway and is secreted intact into bile. There is no information as to the mechanisms that regulate the selection of transport pathway and thereby determine the different metabolic fates for EGF. The experiments reported here were undertaken to determine whether the amount of exogenous EGF administered to the liver (the transport load) might affect the selection of the transport pathway. If ''excess'' EGF, exceeding some as yet undetermined threshold, is preferentially transported by the lysosomal pathway, then the proportion of degraded EGF secreted into bile should increase as a function of the amount of EGF administered. /sup 125/I-EGF (3 to 175 ng) was injected into rat portal veins, and bile samples were collected via cannula. The radioactivity secreted into bile was measured, and the bile samples were immunoprecipitated with anti-EGF antiserum. The proportion of intact vs. degraded EGF in bile was determined by the percentage of immunoprecipitable radioactivity. Regardless of the amount of EGF injected, the pattern of its secretion was unaltered. The percentage of immunoprecipitable EGF in bile was the same for all doses. Therefore, the amount of EGF that was degraded did not change as a function of EGF concentration, implying that the lysosomal pathway was not preferentially utilized as the transport load increased.

• Research Organization: Veterans Administration Medical Center, San Francisco, CA
• OSTI ID: 5411222
• Journal Information: Hepatology (N.Y.); (United States), Journal Name: Hepatology (N.Y.); (United States) Vol. 5:2; ISSN HEPAD
• Country of Publication: United States
• Language: English

Related Subjects

550201* -- Biochemistry-- Tracer Techniques
59 BASIC BIOLOGICAL SCIENCES
ANIMALS
BETA DECAY RADIOISOTOPES
BILE
BIOCHEMISTRY
BIOLOGICAL MATERIALS
BIOLOGICAL PATHWAYS
BODY
BODY FLUIDS
CELL CONSTITUENTS
CHEMISTRY
DAYS LIVING RADIOISOTOPES
DIGESTIVE SYSTEM
ELECTRON CAPTURE RADIOISOTOPES
GLANDS
HORMONES
INTERMEDIATE MASS NUCLEI
IODINE 125
IODINE ISOTOPES
ISOTOPE APPLICATIONS
ISOTOPES
LABELLED COMPOUNDS
LIVER
LYSOSOMES
MAMMALS
MATERIALS
METABOLISM
NUCLEI
ODD-EVEN NUCLEI
ORGANOIDS
ORGANS
RADIOISOTOPES
RATS
RODENTS
TRACER TECHNIQUES
VERTEBRATES