In vivo behavior of human radioiodinated antithrombin III: distribution among three physiologic pools
It has recently been shown that antithrombin III (AT) distributes between plasma, a noncirculating vascular-associated pool and an extravascular pool in rabbit. Study of the in vivo behavior of autologous human /sup 131/I-AT demonstrates that in humans AT also distributes among three pools that are analogous to those found in rabbit. From the in vivo kinetic behavior of the /sup 131/I-labeled AT, the fractions of total-body AT in the plasma, noncirculating vascular-associated, and extravascular pools were calculated to be 0.393 +/- 0.015, 0.109 +/- 0.016, and 0.496 +/- 0.014, respectively. From three-exponential plasma radioactivity disappearance curves, an average plasma fractional catabolic rate, j3, of 0.576 +/- 0.034 day-1 was obtained for five healthy young men. This is almost identical to the result obtained if plasma /sup 131/I-AT disappearance is assumed to fit a two-exponential curve (0.546 +/- 0.038), where the constant C2 from *Ap(t) = C1e-a1t + C2e-a2t is assumed to be equal to 1 - C1. The fraction of the total vascular AT catabolized daily, j3.5, was calculated to be 0.457 +/- 0.034, and the fractional catabolic rate of total-body AT, jT, averaged 0.2271 +/- 0.0176. The results give further support to a model of in vivo behavior in which the vascular AT distributes between plasma and an endothelial receptor. Thus, the latter may serve to mediate activation of AT for its reaction with coagulation proteases and to mediate its entrance into the endothelial cell, where it is either transported to the extravascular fluids or is catabolized.
- Research Organization:
- Univ. of New Mexico School of Medicine, Albuquerque
- OSTI ID:
- 5221312
- Journal Information:
- Blood; (United States), Journal Name: Blood; (United States) Vol. 1; ISSN BLOOA
- Country of Publication:
- United States
- Language:
- English
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59 BASIC BIOLOGICAL SCIENCES
ANIMALS
ANTICOAGULANTS
BETA DECAY RADIOISOTOPES
BETA-MINUS DECAY RADIOISOTOPES
BIOCHEMICAL REACTION KINETICS
BIOLOGICAL MATERIALS
BLOOD
BLOOD PLASMA
BODY FLUIDS
CATABOLISM
DAYS LIVING RADIOISOTOPES
DISTRIBUTION
DRUGS
ENZYMES
EXTRACELLULAR SPACE
HEMATOLOGIC AGENTS
HYDROLASES
IN VIVO
INTERMEDIATE MASS NUCLEI
IODINE 131
IODINE ISOTOPES
ISOTOPE APPLICATIONS
ISOTOPES
KINETICS
LABELLED COMPOUNDS
MAMMALS
MAN
MATERIALS
MATHEMATICAL MODELS
METABOLISM
NUCLEI
ODD-EVEN NUCLEI
PEPTIDE HYDROLASES
PRIMATES
RADIOISOTOPES
REACTION KINETICS
SPACE
TISSUE DISTRIBUTION
TRACER TECHNIQUES
VERTEBRATES