Feb 1, 1976

Cyclic AMP-dependent and independent inhibition of lipolysis by adenosine and decreased pH

Acta Physiologica Scandinavica
P Hjemdahl, Bertil B Fredholm


NA-stimulated lipolysis and cAMP formation in isolated rat fat cells is inhibited by acidosis. In the present report we have examined the quantitative relationship between lipolysis and cAMP formation at normal and reduced pH and the possible involvement of adenosine, an endogenous inhibitor of cAMP formation. Adenosine antagonized cAMP accumulation and to a considerably lower degree lipolysis, effects potentiated by acidosis. Theophylline, an antagonist of adenosine effects, stimulated lipolysis and cAMP-accumulation, and potentiated responses to NA. Adenosine deaminase (ADA) had theophylline-like effects. Acidosis inhibited lipolysis and cAMP accumulation induced by ADA and theophylline to a larger extent than those induced by NA. It is suggested that adenosine modulates fat cell cAMP production and may contribute to the antilipolytic effect of acidosis. There was a curvilinear relationship between cAMP elevation and glycerol production in fat cell suspensions, which was different at pH 7.4 and at pH 6.6. The amount of cAMP needed for half-maximal activation of lipolysis increased from 1.3 (pH 7.4) to 3.1 pMol X 10(-5) cells (pH 6.6). The maximal glycerol production was reduced from 1 300 to 900 nMol X 10(-5) cells. The antil...Continue Reading

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Mentioned in this Paper

Antagonist Muscle Action
Cyclic AMP
Norepinephrine, (+, -)-Isomer
Cyclic Adenosine Monophosphate Measurement
Lipid Mobilization
Cyclic AMP, (R)-Isomer
Drug Interactions

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