Influence of local blood flow on glycerol levels in human adipose tissue.

The influence of blood flow on adipose tissue glycerol levels was investigated in human subcutaneous adipose tissue in situ, with the aid of microdialysis of the extracellular water space. The concentration of tissue-derived glycerol and the escape of ethanol from the dialysis solvent into the extracellular space were simultaneously monitored; the latter was used as an index of local blood flow around the probe. Selective vasodilation with nitroprusside or hydralazine rapidly reduced the concentration of glycerol by 50% and at the same time increased the escape of ethanol (P < 0.001). Stimulation of local blood flow and lipolysis with the beta-adrenoceptor agonist isoprenaline caused an increase in ethanol escape (P = 0.01) and a 100% rise in the dialysate glycerol level (P = 0.001). When vasodilation was first induced by nitroprusside, the subsequent addition of isoprenaline to the microdialysate perfusate caused no change in the concentration of glycerol in adipose tissue but a slight increase in ethanol escape. In conclusion, local blood flow plays an important role in the regulation of the glycerol level in human adipose tissue. Stimulation of blood flow may under certain conditions decrease the level of glycerol in the extracellular space of adipose tissue although the mobilization of glycerol from fat cells to this compartment is increased. Thus, changes in blood flow and glycerol should be considered together when adipose tissue lipolysis is investigated by microdialysis.