Microdialysis of adipose tissue during surgery: effect of local alpha- and beta-adrenoceptor blockade on blood flow and lipolysis.

The adrenergic regulation of adipose tissue lipolysis and blood flow was investigated in nonobese patients (10 men and 23 women) undergoing cholecystectomy. Two microdialysis probes were inserted into the scadipose tissue and microdialyzed in the absence or presence of 10(-4) mol/L of either nonselective beta-adrenoceptor blocker propranolol or nonselective alpha-adrenoceptor blocker phentolamine. The catecholamines increased rapidly after intubation and subsequent surgery and extubation (P = 0.0001; F = 11-13). In the middle of surgery, the elevations of the noradrenaline and adrenaline levels were almost 3 times the basal value. At the end of surgery, they dropped in parallel, but increased again, only to reach their absolute maximum in connection with extubation (10- and 3-fold elevation, respectively). Plasma glycerol and free fatty acids started to increase about 30 min after plasma catecholamines. These increases in catecholamines were paralleled by an increase in the dialysate glycerol level (lipolysis index). Propranolol inhibited by two thirds (P = 0.003) and phentolamine further stimulated by 25% (P = 0.04) the increase in glycerol in the tissue dialysate induced by the operation. There was a transient decrease in tissue blood flow (ethanol escape from the microdialysis probe; P < 0.001) at the beginning of the surgical procedure. This was not affected by propranolol or phentolamine. In conclusion, during anesthesia and surgical trauma, endogenous catecholamines modulate adipose tissue lipolysis via alpha- and beta-adrenoceptors. However, the vasoconstriction induced by these procedures seems to be independent of the adrenergic system.