Journal of Lipid Research, Vol 29, 1637-1642, Copyright © 1988 by Lipid Research, Inc.
25-Hydroxylation of vitamin D3 in the human hepatoma cell lines Hep G2 and Hep 3B
SP Tam, S Strugnell, RG Deeley and G Jones
Department of Biochemistry, Queen's University, Kingston, Ontario, Canada.
Two human hepatoma cell lines, Hep G2 and Hep 3B, were screened for vitamin
D3-25-hydroxylase enzyme activity by incubation with radioactive vitamin
D3. A compound co-chromatographing with 25-OH-D3 was synthesized in both
cell lines but its rate of synthesis was tenfold greater in Hep 3B than in
Hep G2 cells. The identity of the compound was confirmed by comparing its
chromatographic properties with authentic 25-OH-D3 on three different high
pressure liquid chromatography systems. Its production was suppressed by
adding fetal calf serum (10%), lipoprotein-deficient fetal calf serum, or
pure vitamin D-binding globulin to the medium. The mechanism of action of
these plasma proteins appears to involve retardation of uptake of the
substrate. These two cell lines offer considerable potential as defined in
vitro models for studying the effects of physiological factors on the
25-hydroxylation of vitamin D3.
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