Role of adenosine in adipose tissue circulation

Abstract

The vasodilatory effect of adenosine and some related compounds were studied in [dog] subcutaneous adipose tissue in situ. The effects of 3 drugs that inhibit adenosine elimination; 2 adenosine uptake blockers, dipyridamole and dilazep, the adenosine deaminase inhibitor EHNA [erythro-9-(2-hydroxy-3-nonyl)adenosine hydrochloride] were also studied. Plasma levels of adenosine were simultaneously determined by HPLC [high pressure liquid chromatography]. Adenosine was a potent vasodilator and 2- and 6-substituted analogues were even more potent. Tissue blood flow was linearly related to the venous plasma concentrations of adenosine. An elevation of adenosine in plasma from 0.25 to 0.5 .mu.M enhanced blood flow by approximately 50%. A further increase to 1 .mu.M was associated with a doubling of adipose tissue blood flow. Adenosine increased the vascular conductance and the capillary filtration coefficient, indicating that it is active on all sections of the vascular bed. Theophylline and caffeine (30-100 .mu.M in arterial plasma) antagonized the vasodilatory effect of exogenous adenosine, abolished vasodilatation due to EHNA+dipyridamole and reduced resting blood flow. Adenosine probably plays a physiological role in regulating adipose tissue blood flow.