LIPOLYSIS AND LACTATE PRODUCTION IN HUMAN SKELETAL-MUSCLE AND ADIPOSE-TISSUE FOLLOWING GLUCOSE-INGESTION

1. Using microdialysis, we compared lipolysis, as well as the producti on of lactate, in human adipose tissue and muscle after the ingestion of carbohydrate.2. The absolute concentrations of glycerol and lactate were measured in subcutaneous adipose tissue, skeletal muscle and art erialized venous blood in eight normal subjects during basal condition s and 4h after a 75 g oral glucose load, Nutritive blood flow in muscl e and adipose tissue was monitored simultaneously with the microdialys is ethanol clearance technique. 3. At baseline, the concentrations of glycerol in adipose tissue and in muscle were about 7 times and about 2.5 times higher respectively than those in plasma, After glucose inge stion, the changes in glycerol concentrations differed significantly b etween the three compartments (P < 0.0001). In plasma and adipose tiss ue, the concentrations decreased rapidly and markedly, but returned to baseline levels after 4 h. In muscle, the decrease in glycerol was le ss pronounced and more protracted. 4. At baseline, the concentrations of lactate in muscle and in adipose tissue were about 3 times and abou t 1.5 times higher respectively than those in plasma, After the ingest ion of glucose, the levels increased transiently in similar ways in mu scle, adipose tissue and plasma, The differences in absolute lactate c oncentrations between the three compartments were maintained after the glucose load (P < 0.001). 5. Adipose tissue blood flow increased tran siently after glucose ingestion, whereas muscle blood flow remained un changed. 6. Both muscle and adipose tissue are a source of glycerol an d lactate release during basal conditions and after glucose ingestion, The regulation of lactate production, but not of lipolysis, after car bohydrate ingestion is similar in the two tissues.