The conversion of octanoate-l-Cl4 to radioacetoacetate and the effect of pyruvate on this process are dependent on the K+ concentration in the incubation medium (1). These results prompted this investigation in which the incorporation of octanoate-l-Cl4 into fatty acids and cholesterol was determined in the presence of non-radioactive additions of pyruvate, succinate, and fumarate. Malonate was used as an aid in evaluating the relationship between the simultaneous metabolism of octanoate and

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... de novo synthesis of fatty acids. The lipogenic effects of high and low K+ concentrations in the medium were also studied. EXPERIMENTAL Treatment of Animals-Male rats,l with a mean body weight of 200 =t 22 gm., were used in these studies and were fed a stock diet? ad libitum for varying periods of time. The rats were sacrificed by a sharp blow on the head and their livers were quickly excised. Liver slices were prepared free-hand with a thin razor blade. Incubation Procedure-The incubation procedure has been described in an earlier publication from this laboratory (2). Octanoate-l-Cl4 (1.51 mM per liter, final concentration) was added to each flask. The final concentrations of the other additions were as follows: Na pyruvate, Na succinate, and Na fumarate, 7.75 mM per liter, and for Na malonate 5.84 mM per liter. The composition of the media employed will be found in Tables I and II . The high K+ medium contained 70 m.eq. per liter, final concentration, while the corresponding value for the low K+ medium was 7 m.eq. per liter. Analytical Procedure; Respired C1402-Following incubation, the vial containing KOH for carbon dioxide absorption was removed and immediately stoppered. Aliquots of the alkaline solution were mounted directly