Respiration in Isolated Fat Cells and the Effects of Epinephrine

Abstract

1. A technique was devised for ready sequential sampling of lipocyte suspensions for measurement of metabolic activities. 2. With the use of this technique in paired incubations, an effect of oligomycin to decrease the QO2 of fat cells to 45% of control was shown. 3. An analogy between the effect of oligomycin on intact cells and that described for isolated mitochondria was suggested, since the antibiotic inhibited incorporation of 32Pi into acid-soluble mononucleotides and decreased 14CO2 production from glucose-1-14C and glucose-6-14C. 4. Stimulation of QO2 by epinephrine was shown in the presence and in the absence of oligomycin; there was no accompanying increase in 14CO2 production from glucose when oligomycin was present, indicating that glucose was not the substrate for the observed increase in oxygen consumption. 5. It is concluded that oligomycin inhibits oxidative phosphorylation in the fat cell. Under these conditions, (a) a significant portion of the respiration of the lipocyte is not linked in an obligatory fashion to phosphorylation, and (b) it may be inferred that the calorigenic effect of epinephrine in adipose tissue involves electron flow to oxygen not linked to phosphorylation.