Abstract
The inhibitory effect of hypocholesteraemic agents, 1-{2-[4'-(trifluoromethyl)-4-biphenyloxy] ethyl} pyrrolidine (Boxidine) and trans-1,4-bis-(2-chlorobenzylaminomethyl)-cyclohexane dihydrochloride (AY-9944), was studied on the Δ^<5,7>-sterol-Δ^7-reductase in rat liver. (1) Oral administration of Boxidine or AY-9944 resulted in the decrease of serum cholesterol and Δ^<5,7>-sterol-Δ^7-reductase activity. (2) Δ^<5,7>-Sterol-Δ^7-reductase was inhibited by Boxidine and AY-9944 also in vitro. (3) It was required, microsomes, cytoplasmic fraction (or sterol carrier protein=SCP) and NADPH to observe the enzymatic activity. Microsomes were affected by Boxidine and AY-9944. However, the binding of 7-dehydrocholesterol (7-DHC) to SCP was not influenced by these drugs, although vitamin D_3 decreased the Δ^<5,7>-sterol-Δ^7-reductase activity through the inhibition of the binding of 7-DHC to SCP. From these results, the possibility of Boxidine and AY-9944 was discussed in terms of tools for the study of the conversion of 7-DHC to vitamin D_3 in biological system.
