AJP - Endocrinology and Metabolism, Vol 245, Issue 4 326-E331, Copyright © 1983 by American Physiological Society
Plasma clearance, transfer, and distribution of vitamin D3 from intestinal lymph
S. Dueland, P. Helgerud, J. I. Pedersen, T. Berg and C. A. Drevon
The clearance of vitamin D3 from plasma after intravenous injection to rats
of intestinal lymph labeled in vivo with radioactive vitamin D3 has been
studied. The half-life of the injected vitamin D3 was about 6 min. In
double-label experiments the half-life was the same for vitamin D3 as for
vitamin A, which is removed from the circulation as chylomicron remnants.
Fractionation of the blood plasma according to the density showed that 2
min after the injection of the lymph 30-95% of the radioactive vitamin D3
was recovered in plasma fractions with higher densities than chylomicron
remnants (d greater than 1.019 g/ml). The percentage of vitamin D3 in the
chylomicron fraction (d less than 1.006 g/ml) of the injected lymph was
66-95%. Taking this into account it could be calculated that the amount of
radioactive vitamin D3 transferred from chylomicrons or chylomicron
remnants to plasma with d greater than 1.019 g/ml within 2 min varied from
26 to 72%. The transferred radioactivity was recovered in a protein
fraction with chromatographic mobilities identical to the binding protein
for vitamin D and its metabolites. During the first 13 min after injection
the amount of radioactivity recovered in the liver was less than 10%, but
from 15 to 55 min the amount increased to about 50% of the injected dose.
These findings suggest that the transfer of vitamin D3 from chylomicrons to
the alpha-globulin fraction previously observed in vitro is of importance
for the in vivo handling of vitamin D3.(ABSTRACT TRUNCATED AT 250 WORDS)
