Wf. Prigge et al., THYROID-HORMONE IS REQUIRED FOR DIETARY FISH-OIL TO INDUCE HYPERSECRETION OF BILIARY CHOLESTEROL IN THE RAT, Lipids, 30(9), 1995, pp. 833-838
In the rat, both fish oil diet and thyroid hormone replacement are rep
orted to augment bile cholesterol secretion out of proportion to bile
flow or secretion of other bile lipids. We sought common mechanisms fo
r these effects and evaluated the role of phospholipid fatty acid comp
osition in the process. Methimazole-treated hypothyroid rats were fed
low-fat chow or chow supplemented with 10% corn oil or fish oil, and w
ere studied before and after thyroid hormone treatment. Serum, hepatic
, and bile lipids were measured, phospholipid fatty acid composition d
etermined, and hepatic 3-hydroxy-3-methylglutaryl CoA reductase activi
ty assayed. Fish oil diet stimulated cholesterol secretion into bile o
nly after thyroid hormone was given, and this action was synergistic w
ith that of thyroid hormone. Reduced serum cholesterol in fish oil-tre
ated rats was associated with increased biliary cholesterol secretion
and diminished hepatic cholesterol content. This suggests that augment
ed biliary cholesterol secretion may contribute to the fish oil-induce
d reduction of serum cholesterol. No definite relationship between hep
atic or biliary phospholipid fatty acid composition and biliary secret
ion was apparent, although high bile cholesterol secretion was associa
ted with a low percentage of hepatic and bile phospholipid linoleic ac
id.