Factors affecting fatty acid oxidation in fat cells isolated from rat white adipose tissue.

Eat cells isolated from rat epididymitl itdipose tissue were incubated with albumin-bound ( **C)palmitate. Incorporation of '*C into '*CO, and glycerides w;ts measured. Some evidence is presented to suggest that the exogenous palmitate pool is in isotopic equilibrium with intracellular precursors for these metabolic processes. Precautions were taken to minimize dilution of the exog- enous palmitate pool by fatty acids released from the cells. 14C;02 production from ( l-'4C)palmitate was 3 times that from ( 16-'*C)palmitate. Octanoate increased this diffcren- tial oxidation of palmitate carbons and also inhibited palmitate oxidation without similarly affecting esterifica- tion. Glucose increased palmitate esterification in cells from fed or starved rats. Insulin potentiated this effect of glucose. Glucose influenced palmitate oxidation in a inore complex manner, dependent upon the glucose concen- tration. Both the observation that esterification con- stitutes 99% of the metabolic flux of fatty acid and the manner in which glucose, insulin, or st;trv;ttion influence palmitate esterification and oxidation suggested that tiictors controlling esterification may alter oxidation as ;I secondary effect, but not vice versa. It is suggested that oxidation and esterification compete for a single intracellulai- pre- cursor, possibly extramitochondrial long chain fatty acyl COA.