Changes in ATP and Cyclic Nucleotide Levels during Sympathetic Nerve Stimulation in Canine Subcutaneous Adipose Tissue in situ

Abstract

Subcutaneous adipose tissue in fed, female dogs was isolated. Biopsies of the tissue (30-150 mg) were taken and rapidly frozen in liquid N2 before, during and after nerve stimulation (3-4 Hz). In unstimulated adipose tissue, the levels of ATP were 74 .+-. 7 nmol/g, of cyclic[c]AMP 90 .+-. 12 pmol/g and of cGMP 18 .+-. 3 pmol/g (mean .+-. SE). During sympathetic nerve stimulation the level of ATP and cGMP fell by 30 and 50%, respectively, (P < 0.01), while the cAMP content increased by 50% (P < 0.05). After nerve stimulation, there was a marked increase in glycerol release, and the levels of all 3 nucleotides returned to control. The fall in ATP during nerve stimulation was essentially eliminated by prior adrenergic .alpha.-receptor blockade. Sympathetic nerve stimulation apparently induces a rapid, reversible fall in tissue ATP content, which may be related to hypoxia secondary to the vasoconstriction. Lipolytic responses to sympathetic nerve stimulation in vivo are preceeded by small increases in the tissue cAMP level and a 3-fold increase in the cAMP/cGMP ratio.