MODULATION OF VASCULAR TONE AND GLYCEROL LEVELS MEASURED BY IN-SITU MICRODIALYSIS IN RAT ADIPOSE-TISSUE

Changes in blood flow induced by the beta-adrenoceptor agonist isoprot erenol(Iso) and a stable analogue of the major metabolite of arachidon ic acid in adipose tissue, carbaprostacyclin (cPGI(2)), have been stud ied in rat periepididymal fat pad with in situ microdialysis by measur ing the distribution ratio of 0.2% ethanol in the dialysate (outflow) to that in the perfusate (inflow) (O/I ratio). Local perfusions of 1 m u M cPGI(2) or 1 mu M Iso led to reversible decreases of the O/I ratio that were similar to the decrease induced by the vasodilating referen ce drug hydralazine (Hydra, 630 mu M) Interestingly, a continuous perf usion of Hydra at a submaximal vasodilating concentration (63 mu M) wa s sufficient to prevent further vasodilatation induced by Iso or cPGI( 2). To take advantage of this observation, experiments were designed t o evaluate the influence of the vasodilating effect of Iso or cPGI(2) on the ability of either to induce lipolysis in vivo. The results show ed that the vasodilating effect of Iso could contribute to glycerol re moval from the extracellular fluid and demonstrated that cPGI(2) was d evoid of lipolytic activity.