Incorporation of [3H]acetate into L-cell lipids. Dependence on method of linoleate administration and timing of the pulse label.
An aqueous solution containing 5 mumol of sodium linoleate was supplied to cultures of L-fibroblasts by two methods: (a) direct addition to the culture as a single dose at the start of a 48 h incubation period (method I); or (b) infusion into the culture at a constant rate throughout the same time period (method II). At 23 h and 47 h the cells were subjected to a 1 h pulse of [3H]acetate. At 23 h method I was 1.2-times as effective as method II in reducing incorporation of radioactive label into cell sterol. Conversely, the decrease in utilization of [3H]acetate for acyl group biosynthesis was 1.7-times greater by method II than by method I. At 47 h both methods had similarly reduced [3H]acetate incorporation into both fractions by 85%. Regardless of the method used for supplementation, the large decline in biosynthesis from [3H]acetate noted at 47 h was not accompanied by any corresponding decrease in the total amount of sterol synthesized. Additional data suggest that 50% of more of the decrease in [3H]acetate incorporation at this time may be attributable to metabolites derived from the unlabeled exogenous fatty acid, which act to dilute the radioactively labeled tracer and/or to inhibit endogenous lipid biosynthesis.
D000085:Acetates / Q000378:metabolism*; D000818:Animals; D005410:Flame Ionization; D007700:Kinetics; D007739:L Cells / Q000378:metabolism; D019787:Linoleic Acid; D008041:Linoleic Acids / Q000378:metabolism*; D008055:Lipids / Q000096:biosynthesis*; D051379:Mice; D014316:Tritium
D000085:Acetates; D008041:Linoleic Acids; D008055:Lipids; D014316:Tritium; D019787:Linoleic Acid