AJP - Regulatory, Integrative and Comparative Physiology, Vol 252, Issue 3 457-R461, Copyright © 1987 by American Physiological Society
Distribution of antithrombin III in rabbits: role of host and protein
E. Regoeczi
Unlike in the case of some other species, the plasma curve of
iodine-labeled antithrombin III (I-AT-III) in rabbits requires fitting with
a three-term exponential function for obtaining reliable estimates of the
catabolic rate and distribution of I-AT-III among various body compartments
(Carlson, Atencio, and Simon. J. Clin. Invest. 74: 191-199, 1984). To
decide whether this phenomenon is referable to the host or the protein, the
behavior of rabbit and human I-AT-III was comparatively analyzed in
rabbits. Data obtained with rabbit I-AT-III confirmed the findings by
Carlson and co-workers. Human I-AT-III assumed a distribution that closely
paralleled that of homologous I-AT-III, thus suggesting that the pattern of
distribution is determined by the host species rather than its AT-III.
Rabbits metabolized human I-AT-III 1.61 times faster than homologous
I-AT-III by an unknown mechanism not involving immune response; a facet
that may prove useful for the identification of the sites of catabolism of
AT-III. The exponent of the body weight was calculated for the relationship
between species size and AT-III turnover. A value of 0.5 was obtained that
is distinctly lower than the exponents found earlier for some other plasma
proteins.
