Why do total-body decay curves of iodine-labeled proteins begin with a delay
The initial delay that occurs in total-body radiation curves reaching their single-exponential slopes was analyzed from 106 experiments involving several mammalian species (guinea pig, mouse, rabbit, and rat) and plasma proteins (alpha 1-acid glycoprotein, antithrombin III, fibrinogen, immunoglobulin G, and transferrin) in 14 different combinations. The time interval (Td) between injection and the intercept of the slope with the full-dose value was adopted as a measure of curve nonideality. The overall mean Td was 6.6 h, but individual values showed a significant correlation to protein half-lives, whereby proteins of unequal metabolic properties exhibited different mean Td values. Targeting protein to the liver abolished delay. Choice of the isotope (/sup 125/I or /sup 131/I) and size of the labeled protein had no influence on the magnitude of delay. Whole-body radiation curves of animals that received (/sup 125/I)iodotyrosines, Na/sup 131/I, or /sup 131/I-polyvinylpyrrolidone exhibited no initial delays. These results do not support the earlier notion that delay is caused by a redistribution of the labeled protein in the body to radiometrically more favorable sites. However, they are compatible with the assumption that delayed passage of a protein dose through the extracellular matrix and/or retarded transfer of proteolytic products from extravascular catabolic sites to plasma may be responsible for the phenomenon.
- Research Organization:
- McMaster Univ. Health Sciences Centre, Hamilton, Ontario
- OSTI ID:
- 6018766
- Journal Information:
- Am. J. Physiol.; (United States), Journal Name: Am. J. Physiol.; (United States) Vol. 253; ISSN AJPHA
- Country of Publication:
- United States
- Language:
- English
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63 RADIATION, THERMAL, AND OTHER ENVIRON. POLLUTANT EFFECTS ON LIVING ORGS. AND BIOL. MAT.
AMIDES
AMINO ACIDS
ANIMALS
AZOLES
BETA DECAY RADIOISOTOPES
BETA-MINUS DECAY RADIOISOTOPES
BIOLOGICAL HALF-LIFE
BLOOD COAGULATION FACTORS
CARBOHYDRATES
CARBOXYLIC ACIDS
COAGULANTS
DAYS LIVING RADIOISOTOPES
DRUGS
ELECTRON CAPTURE RADIOISOTOPES
EXTERNAL IRRADIATION
FIBRINOGEN
GLOBULINS
GLOBULINS-BETA
GLUCOPROTEINS
GUINEA PIGS
HEMATOLOGIC AGENTS
HEMOSTATICS
HETEROCYCLIC COMPOUNDS
HYDROXY ACIDS
IMMUNOGLOBULINS
INTERMEDIATE MASS NUCLEI
IODINE 125
IODINE 131
IODINE ISOTOPES
IRRADIATION
ISOTOPES
LACTAMS
MAMMALS
MEMBRANE TRANSPORT
METABOLISM
METALLOPROTEINS
MICE
NUCLEI
ODD-EVEN NUCLEI
ORGANIC ACIDS
ORGANIC COMPOUNDS
ORGANIC NITROGEN COMPOUNDS
PROTEINS
PYRROLES
PYRROLIDONES
RABBITS
RADIOISOTOPES
RATS
RODENTS
SACCHARIDES
TRANSFERRIN
TYROSINE
VERTEBRATES
WHOLE-BODY IRRADIATION