Feb 1, 1976

Inhibition by acidosis of adenosine 3',5'-cyclic monophosphate accumulation and lipolysis in isolated rat fat cells

Acta Physiologica Scandinavica
B B Fredholm, P Hjemdahl

Abstract

Lipolysis and cyclic AMP accumulation were studied in isolated rat fat cells at normal (7.4) and decreased (7.0, 6.6) pH. Acidosis inhibited lipolysis and cyclic AMP accumulation due to NA non-competetively. Maximal lipolysis (3 muM NA) was inhibited by 25% at pH 7.0 and by 61% at pH 6.6 Cyclic AMP accumulation 5 min after 3 muM NA was inhibited by 57% at pH 7.0 and by 83% at pH 6.6. Between 10 and 60 minutes of incubation NA-stimulated lipolysis was linear at pH 7.4, whereas a progressively increasing inhibition was seen at lower pH. The FFA production was inhibited to the same degree as glycerol production by acidosis. The fraction of FFA associated with the cells was the same at all pHs. Thus, we have no evidence that acidosis inhibits lipolysis via accumulation of FFA intracellularly. NA-induced accumulation of 3H-cAMP from 3H-ATP, endogenously formed by prelabelling the cells with 3H-adenine, was inhibited by acidosis both in the presence and absence of theophylline in the incubation medium (by 48 and 44% respectively at pH 7.0 and by 74 and 68% at pH 6.6). Cyclic nucleotide phosphodiesterase in homogenates of fat cells was inhibited by decreasing the pH, whether measured at high or low substrate concentrations. Basal aden...Continue Reading

  • References19
  • Citations16

References

  • References19
  • Citations16

Citations

Mentioned in this Paper

Glycerin
Adenosine
Membrane Fraction
Cyclic AMP
Norepinephrine, (+, -)-Isomer
Cyclic Adenosine Monophosphate Measurement
Saturated Fat
Lipid Mobilization
Cyclic AMP, (R)-Isomer
Theophylline

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