Journal of Lipid Research, Vol 31, 2179-2185, Copyright © 1990 by Lipid Research, Inc.
Oxygenation of desmosterol and cholesterol in cell cultures
SE Saucier, AA Kandutsch, AK Gayen, JA Nelson and TA Spencer
Jackson Laboratory, Bar Harbor, ME 04609.
In order to determine whether hydration of the delta 24 bond of desmosterol
contributes to the formation of the regulatory oxysterol,
25-hydroxycholesterol, [3H]desmosterol was incubated with two cultured cell
lines and the labeled products were analyzed. Small amounts of 25-
hydroxycholesterol were formed with Chinese hamster lung (Dede) cell
cultures, but not with mouse fibroblast (L) cell cultures. Apparently,
desmosterol was converted into cholesterol, a process that does not occur
in L cells, before 25-hydroxycholesterol takes place. No reliable evidence
could be obtained for hydration of the delta 24 bond or for the reverse
reaction upon incubation of [3H]25-hydroxycholesterol. Oxygenation of
desmosterol occurred in both Dede and L cell cultures to give a mixture of
24(R)- and 24(S)-25-epoxy-cholesterol. This reaction, along with the
production of 7-oxygenated sterols, may account for low levels of HMG-CoA
reductase repressor activity previously found to be associated with delta
24 sterols.
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