Repeated estimation of liver cholesterol synthesis in vivo using the inhibitor AY-9944

1. 1. We have examined the validity and usefulness of an assay for liver cholesterol synthesis using the inhibitor AY-9944, which inhibits only the conversion of 7-dehy-drocholesterol to cholesterol. 2. 2. In rats treated with a single dose of AY-9944 the level of 7-dehydrocholesterol in the blood 24 h after treatment is representative of the cholesterol which would have been synthesised by the liver had the inhibitor not been present. 3. 3. The assay has been tested under a variety of conditions known to alter liver cholesterol synthesis, and was found to correlate closely with values obtained when liver synthesis was measured in vitro. 4. 4. Consistent results were obtained with repeated assays, which can be carried out at weekly intervals on the same animals. © 1971.