In order to determine the feasible role of monooxygenases in regulation of the macrophage acyl-CoA: cholesterol acyltransferase (ACAT) activity, the effects of ketoconazole on the activities of benz(a)pyrene hydroxylase and ACAT as well as on the [14C]oleate incorporation into cholesterol esters in cultured mouse peritoneal macrophages (MPM) were studied. Ketoconazole (0.5-50 M) inhibited the benz(a)pyrene hydroxylase activity but increased the free cholesterol (FC) level in MPM cultured with an acetylated low density lipoprotein (acetyl-LDL). An addition of ketoconazole (1-50 M) eliminated the increase in the rate of FC esterification after incubation of MPM with acetyl-LDL (but not with 25-hydroxycholesterol). In contrast, progesterone, an ACAT activity inhibitor, used at 5-30 M diminished the rate of FC esterification, when MPM were incubated with acetyl-LDL of 25-hydroxycholesterol. Ketoconazole provoked a dose-dependent decrease of the [3H]FC incorporation into macrophage polar oxysteroids. The data obtained suggest that the ketoconazole (1-30 M) effect on FC esterification in MPM cultured with acetyl-LDL is determined by its inhibiting monooxygenases, which produce oxidized forms of FC that are potential activators of ACAT.
Animals Benzopyrene Hydroxylase