FIGURE 6.

(A) Cell-free (post-mitochondrial) sterol synthesis rates, tumor 3924A vs. normal liver. Post-mitochondrial system (PMS) incubations (4 h, 37°C) contained either [1,5-¹⁴C]-citrate or [1-¹⁴C]-acetate (1.5 μCi/ml, 10 mM), or 10 mM citrate^a or acetate^b in the presence of [³H]-H₂O (5 mCi/ml). Data error bars are means ± SEM. A correction factor of 1.5 was required for calculation of C₂ incorporation into sterol from [1,5-¹⁴C]-citrate or [1-¹⁴C]-acetate because only 12 of the 18 C₂ units supplied are incorporated/mol cholesterol. With the [³H]-H₂O incubations, a correction factor of 0.536 was used, equivalent to the (³H/C) incorporation ratio into cholesterol (14-to-15 [³H]/27 cholesterol carbons) (see: Azrolan and Coleman, 1989, for details on methods). (B) Cell-free (post-mitochondrial) ATP-citrate lyase activity, tumor 3924A vs. normal liver. Data from two complementary procedures on PMS incubation aliquots (4 h, 37°C) are shown (1). Direct ATP-citrate lyase activity (measured as oxaloacetate, OAA formed), and (2) anion exchange-resolved malate generated (plus and minus added malate dehydrogenase, MDH, 2 units/ml, to assure reaction completion). Data error bars are means ± SEM (see: Azrolan and Coleman, 1989, for details on methods).