title: Effect of detergents on in vitro 7 alpha-hydroxycholesterol formation by rat liver microsomes.
abstract: Formation of 7 alpha-hydroxycholesterol by rat liver microsomes was quantitated using a gas chromatograph-mass spectrometer (GC/MS) operated in selected ion monitoring (SIM) mode. Microsomes from normal rat livers incubated for different periods were found to yield increased 7 alpha-hydroxycholesterol with time. This was also true when incubations contained Tween-80, but in this instance, the rate of 7 alpha-hydroxycholesterol production was lower and dependent on the concentration of Tween used. Similarly, Triton X-100, Renex-30, Kyro EOB, Cutscum, and Emulgen 911 all lowered the formation of 7 alpha-hydroxycholesterol by rat liver microsomes, whereas Triton WR-1339 stimulated its production. Analysis of data obtained from following the enzyme reaction over an extended period using an integrated Michaelis-Menten equation indicated the enzyme possesses a very significant affinity for the product (Ks greater than Kp). Similar analysis shows that Tween-80 is a noncompetitive inhibitor of the enzyme.
mesh_terms: D000818:Animals; D003902:Detergents / Q000494:pharmacology*; D008401:Gas Chromatography-Mass Spectrometry; D006888:Hydroxycholesterols / Q000378:metabolism*; D008297:Male; D008433:Mathematics; D008862:Microsomes, Liver / Q000187:drug effects / Q000378:metabolism*; D051381:Rats; D013501:Surface-Active Agents / Q000494:pharmacology*; D013997:Time Factors
chemical_list: D003902:Detergents; D006888:Hydroxycholesterols; D013501:Surface-Active Agents; C011724:cholest-5-en-3 beta,7 alpha-diol