Lactate metabolism of subcutaneous adipose tissue studied by open flow microperfusion

Open flow microperfusion and a novel calibration technique (ionic reference technique) mere evaluated for the frequent measurement of the absolute lac tate concentration in sc adipose tissue. Furthermore, the influence of the plasma insulin concentration on the lactate concentration of sc adipose tis sue was investigated during hyperglycemia. Sixteen lean healthy young men p articipated in the studies. In the postabsorbtive state the mean sc lactate concentrations were 1.29 and 1.36 mmol/L for the ionic reference technique and the no net flux protocol, respectively (not significant, P > 0.05). Th e simultaneously measured arterialized plasma lactate concentration was sig nificantly lower at 0.77 mmol/L (P < 0.05). Both the sc lactate concentrati on (1.8 +/- 0.33 mmol/L) and the plasma lactate concentration (0.96 +/- 0.0 3 mmol/L) were significantly elevated during a hyperinsulinemic euglycemic clamp experiment. During a hyperglycemic clamp experiment the sc lactate co ncentration reached a significantly elevated plateau (2.15 +/- 0.27 mmol/L) that was not influenced by the increasing plasma insulin concentration. It is concluded that 1) open flow microperfusion combined with the ionic refe rence technique enables frequent measurement of the sc lactate concentratio n; 2) sc adipose tissue is a significant source of lactate release in the p ostabsorbtive state as well as during hyperinsulinemic clamp conditions; an d 3) insulin concentrations greater than 180 pmol/L have no further influen ce on adipocyte stimulation of sc adipose tissue with respect to lactate re lease.