Inulin-125I-tyramine, an improved residualizing label for studies on sites of catabolism of circulating proteins
Residualizing labels for protein, such as dilactitol-125I-tyramine (125I-DLT) and cellobiitol-125I-tyramine, have been used to identify the tissue and cellular sites of catabolism of long-lived plasma proteins, such as albumin, immunoglobulins, and lipoproteins. The radioactive degradation products formed from labeled proteins are relatively large, hydrophilic, resistant to lysosomal hydrolases, and accumulate in lysosomes in the cells involved in degradation of the carrier protein. However, the gradual loss of the catabolites from cells (t1/2 approximately 2 days) has limited the usefulness of residualizing labels in studies on longer lived proteins. We describe here a higher molecular weight (Mr approximately 5000), more efficient residualizing glycoconjugate label, inulin-125I-tyramine (125I-InTn). Attachment of 125I-InTn had no effect on the plasma half-life or tissue sites of catabolism of asialofetuin, fetuin, or rat serum albumin in the rat. The half-life for hepatic retention of degradation products from 125I-InTn-labeled asialofetuin was 5 days, compared to 2.3 days for 125I-DLT-labeled asialofetuin. The whole body half-lives for radioactivity from 125I-InTn-, 125I-DLT-, and 125I-labeled rat serum albumin were 7.5, 4.3, and 2.2 days, respectively. The tissue distribution of degradation products from 125I-InTn-labeled proteins agreed with results of previous studies using 125I-DLT, except that a greater fraction of total degradation products was recovered in tissues. Kinetic analyses indicated that the average half-life for retention of 125I-InTn degradation products in tissues is approximately 5 days and suggested that in vivo there are both slow and rapid routes for release of degradation products from cells.
- Research Organization:
- Univ. of South Carolina, Columbia (USA)
- OSTI ID:
- 6544505
- Journal Information:
- J. Biol. Chem.; (United States), Journal Name: J. Biol. Chem.; (United States) Vol. 263:28; ISSN JBCHA
- Country of Publication:
- United States
- Language:
- English
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59 BASIC BIOLOGICAL SCIENCES
ALBUMINS
AMINES
ANIMALS
AROMATICS
AUTONOMIC NERVOUS SYSTEM AGENTS
BETA DECAY RADIOISOTOPES
BIOLOGICAL HALF-LIFE
CARBOHYDRATES
CATABOLISM
DAYS LIVING RADIOISOTOPES
DISTRIBUTION
DRUGS
ELECTRON CAPTURE RADIOISOTOPES
GLOBULINS
HYDROXY COMPOUNDS
IMMUNOGLOBULINS
INTERMEDIATE MASS NUCLEI
INULIN
IODINE 125
IODINE ISOTOPES
ISOTOPE APPLICATIONS
ISOTOPES
LABELLING
LIPIDS
LIPOPROTEINS
MAMMALS
METABOLISM
METABOLITES
MOLECULAR WEIGHT
NUCLEI
ODD-EVEN NUCLEI
ORGANIC COMPOUNDS
PHENOLS
POLYSACCHARIDES
PROTEINS
RADIOISOTOPES
RATS
RODENTS
SACCHARIDES
SYMPATHOMIMETICS
TISSUE DISTRIBUTION
TRACER TECHNIQUES
TYRAMINE
VERTEBRATES