Tonic activity of the rat adipocyte A1-adenosine receptor

British Journal of Pharmacology
Hui-Xiu LiangJohn C Shryock

Abstract

1. Adipocyte A(1)-adenosine receptors (A(1) AdoR) tonically inhibit adenylyl cyclase and lipolysis. Three potential explanations for tonic activity of A(1)AdoR of rat epididymal adipocytes were investigated: high affinity of adenosine for the receptor, efficient coupling of receptor activation to response, and spontaneous activity of the receptor in the absence of agonist. 2. The affinity of adenosine for the adipocyte A(1)AdoR was determined as 4.6 microM by analysis of effects of an irreversible receptor antagonist on agonist concentration-response relationships. In contrast, the potency of adenosine to decrease cyclic AMP in isolated adipocytes was 1.4 nM. 3. Occupancy by agonist of the A(1)AdoR was efficiently coupled to functional response (decrease of adipocyte cyclic AMP content). Activation by adenosine of less than 1% of A(1)AdoRs caused a near-maximal decrease of cyclic AMP in adipocytes. Thus the receptor reserve for adenosine to decrease cyclic AMP content of adipocytes was greater than 99%. 4. Affinities and receptor reserves for other A(1)AdoR agonists were determined. Agonists appeared to differ more in their affinity for the receptor than in their intrinsic efficacy to activate it. 5. A(1)AdoRs were inactive in ...Continue Reading

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Citations

May 12, 2010·International Journal of Obesity : Journal of the International Association for the Study of Obesity·B ZarroukiC O Soulage
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Mar 1, 2014·Journal of Molecular Endocrinology·Thomas Svava NielsenSten Lund
Apr 17, 2014·Frontiers in Neuroendocrinology·Timothy J BartnessVitaly Ryu
Nov 18, 2008·Expert Opinion on Investigational Drugs·Elfatih Elzein, Jeff Zablocki
May 26, 2009·Progress in Lipid Research·Max Lafontan, Dominique Langin
Jan 18, 2006·The Journal of Pharmacology and Experimental Therapeutics·Marjan FatholahiJohn C Shryock
Jan 6, 2007·The Journal of Pharmacology and Experimental Therapeutics·Arvinder K DhallaLuiz Belardinelli
Aug 23, 2011·Pharmacological Reports : PR·Monika Samsel, Krystyna Dzierzbicka
Aug 15, 2012·BioFactors·Andrea EscuderoCarlos Escudero
Mar 16, 2011·Physiological Research·T SzkudelskiK Szkudelska
Sep 16, 2008·European Journal of Pharmacology·Stina M JohanssonBertil B Fredholm
Aug 9, 2011·Life Sciences·Tomasz Szkudelski, Katarzyna Szkudelska

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