Measurement of adipose-tissue metabolites in vivo

1. The concentrations of glucose, pyruvate, lactate, citrate, glutamate, malate and aspartate were measured in epididymal adipose tissue from starved, fed and starved-re-fed rats. 2. To measure these intermediates it was necessary to correct for their concentration in the extracellular tissue space, which was considered to be most satisfactorily equated with the glucose space. This space in vivo was 7.42, 4.90 and 7.54ml./100g. wet wt. of tissue in adipose tissue taken from starved, fed and starved-re-fed rats respectively. After correction for the glucose space, the concentrations of metabolites (nmoles/g. of cells) in epididymal adipose tissue of fed rats were: pyruvate, 8.5; lactate, 50.3; citrate, 18.5; glutamate, 100.0; malate, 6.4; aspartate, 34.2. 3. Starvation for 72hr. resulted in a fall in pyruvate and aspartate concentrations to 3.57 and 25.1nmoles/g.; starvation for 72hr. followed by re-feeding for 72hr. caused an increase in glutamate and aspartate concentrations to 140 and 67.6nmoles/g. 4. These changes are interpreted with regard to the simultaneous alteration in lipogenesis that occurs during the starvation-re-feeding cycle.