Vascular and Metabolic Effects of Theophylline, Dibuturyl Cyclic AMP and Dibuturyl Cyclic GMP in Canine Subcutaneous Adipose Tissue in situ1

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Abstract
In canine subcutaneous adipose tissue theophylline (2×10‐‐4M), cAMP and ATP (10‐‐5M), and DBcAMP (8×10‐‐4M) increased blood flow by by approximately 100 per cent. These compounds also antagonized sympathetic vasoconstriction. Theophylline and DBcAMP increased glycerol release dose‐dependently, while cAMP and ATP were ineffective up to I mM. Theophylline (0.4–0.8 mM) potentiated the lipolytic effect of nerve stimulation, while 2–8 mM apparently caused maximal stimulationPer se. DBcAMP did not affect FFA release following nerve stimulation, while DBcGMP potentiated. The apparent rate of re‐esterification, glucose uptake and lactate release was decreased by theophylline. DBcAMP (0.1–0.4 mM) had no effect on these parameters, while DBcGMP at the same concentration decreased re‐esterification and lactate release. Stimulated overflow of3H from tissues prelabelled with L‐3H‐noradrenaline was reduced to 50 per cent by ATP (0.1–0.4 mM), but was unaffected by DBcAMP and DBcGMP at the same concentration. The results support the view that cAMP mediates the metabolic actions of sympathetic nerve stimulation in canine subcutaneous adipose tissue. The relationship between cAMP and vascular reactions may be more complex.