IN-SITU ASSESSMENT OF THE ROLE OF THE BETA(1)-ADRENOCEPTORS, BETA(2)-ADRENOCEPTORS AND BETA(3)-ADRENOCEPTORS IN THE CONTROL OF LIPOLYSIS AND NUTRITIVE BLOOD-FLOW IN HUMAN SUBCUTANEOUS ADIPOSE-TISSUE

1 The involvement of beta(1)-, beta(2)- and beta(3)-adrenoceptors in t he control of lipolysis and nutritive blood flow was investigated in a bdominal subcutaneous adipose tissue of healthy young adults by use of an in situ microdialysis technique. 2 Dialysis probes were infused ei ther with isoprenaline (non-selective beta-adrenoceptor agonist), CGP 12,177 (selective beta(3)-adrenoceptor agonist having beta(1)-/beta(2) -antagonist properties), dobutamine (selective beta(1)-adrenoceptor ag onist) or terbutaline (selective beta(2)-adrenoceptor agonist). The re covery of each probe used for perfusion was calculated by an in vivo c alibration method. The local blood flow was estimated through the meas urement of the escape of ethanol infused simultaneously with the drugs included in the probe.3 Isoprenaline infusion at 0.01 mu M had a weak effect while higher concentrations of isoprenaline (0.1 and 1 mu M) c aused a rapid, sustained and concentration-dependent increase of glyce rol outflow; the maximum increase was 306 +/- 34% with 1 mu M. Isopren aline also increased the nutritive blood flow in adipose tissue; a sig nificant effect appeared at 0.1 mu M isoprenaline and was greater at 1 mu M. 4 CGP 12,177 (10 and 100 mu M) increased the glycerol concentra tion in the dialysate (128 +/- 8 and 149 +/- 12%, respectively) and nu tritive blood flow. Terbutaline and dobutamine (100 mu M) both provoke d rapid and similar increases in glycerol outflow (252 +/- 18 and 249 +/- 18%, respectively). Both, terbutaline and dobutamine increased nut ritive blood flow. 5 It is concluded that beta(1)- and beta(2)-adrenoc eptor subtypes are both mainly involved in the mobilization of lipids and in the control of nutritive blood flow. beta(3)-Adrenoceptors play a weaker role in the control of lipolysis and nutritive blood flow in human subcutaneous abdominal adipose tissue.