Extracellular cyclic AMP-adenosine pathway in isolated adipocytes and adipose tissue.
OBJECTIVE
Our goal was to evaluate the presence and lipolytic impact of the extracellular cyclic adenosine monophosphate (AMP)-adenosine pathway in adipose tissue.


METHODS
Sixteen miniature Yucatan swine (Sus scrofa) were used for these in vitro and in situ experiments. Four microdialysis probes were implanted into subcutaneous adipose tissue and perfused at 2 microL/min with Ringer's solution containing no addition, varying levels of cyclic AMP, 10 microM isoproterenol, or 10 microM isoproterenol plus 1 mM alpha,beta-methylene adenosine 5'-diphosphate (AMPCP), a 5'-nucleotidase inhibitor. Dialysate was assayed for AMP, adenosine, inosine, hypoxanthine, and glycerol. Freshly isolated adipocytes were incubated with buffer, 1 microM isoproterenol, or 1 microM isoproterenol plus 0.1 mM AMPCP, and extracellular levels of AMP, adenosine, inosine, hypoxanthine, and glycerol were measured.


RESULTS
Perfusion of adipose tissue with exogenous cyclic AMP caused a significant increase in AMP and adenosine appearance. Perfusion with AMPCP, in the presence or absence of isoproterenol, significantly increased the levels of AMP and glycerol, whereas it significantly reduced the level of adenosine and its metabolites. However, the AMPCP-provoked increase in lipolysis observed in situ and in vitro was not temporally associated with a decrease in adenosine.


CONCLUSIONS
These data suggest the existence of a cyclic AMP-adenosine pathway in adipocytes and adipose tissue. The role of this pathway in the regulation of lipolysis remains to be clarified.
Department of Animal and Nutritional Sciences, University of New Hampshire, Durham, NH 03824, USA.
Marci B
MB
Strouch
Edwin K
EK
Jackson
Zaichuan
Z
Mi
Nicole A
NA
Metes
Gale B
GB
Carey
D000241:Adenosine / Q000032:analysis / Q000378:metabolism*; D000249:Adenosine Monophosphate / Q000037:antagonists & inhibitors / Q000378:metabolism; D000255:Adenosine Triphosphate / Q000031:analogs & derivatives / Q000494:pharmacology; D017667:Adipocytes / Q000187:drug effects / Q000378:metabolism*; D000273:Adipose Tissue / Q000187:drug effects / Q000378:metabolism*; D000318:Adrenergic beta-Agonists / Q000494:pharmacology; D000818:Animals; D000242:Cyclic AMP / Q000378:metabolism* / Q000493:pharmacokinetics; D005260:Female; D005990:Glycerol / Q000378:metabolism; D019271:Hypoxanthine / Q000378:metabolism; D007288:Inosine / Q000378:metabolism; D007545:Isoproterenol / Q000494:pharmacology; D008066:Lipolysis / Q000187:drug effects / Q000502:physiology; D008297:Male; D013552:Swine; D013556:Swine, Miniature
D000318:Adrenergic beta-Agonists; D019271:Hypoxanthine; D000249:Adenosine Monophosphate; D007288:Inosine; D000255:Adenosine Triphosphate; D000242:Cyclic AMP; D000241:Adenosine; D007545:Isoproterenol; C002630:alpha,beta-methyleneadenosine 5'-triphosphate; D005990:Glycerol