Original Article

Stress-induced alteration in the lipolytic response to ß-adrenoceptor agonists in rat white adipocytes

Correspondence to: Regina Célia Spadari-Bratfisch

We analysed the sensitivity to ß-adrenoceptor agonists in epididymal adipose cells from rats submitted to a stress protocol previously reported to induce alterations in sensitivity to catecholamines in cardiac tissue from rats. Food intake and body weight were lower, whereas adipocytes basal lipolysis was higher (control: 0.59 ± 0.04; stress: 1.00 ± 0.11, µmol glycerol/100 mg total lipids/100 min) in stressed compared to control rats. The responses to isoprenaline (pD₂ control: 7.46 ± 0.11; stress: 8.11 ± 0.17), adrenaline (pD₂ control: 5.78 ± 0.20; stress: 6.13 ± 0.18), and salbutamol (pD₂ control: 5.64 ± 0.28; stress: 5.92 ± 0.34) were sensitized, and the lipolytic responses to norepinephrine (pD₂ control: 6.98 ± 0.13; stress: 6.41 ± 0.12) and to BRL37344 (pD₂ control: 8.43 ± 0.19; stress: 7.54 ± 0.21) were desensitized. Responses to the higher concentration (100 µM) of isoprenaline (control: 1.80 ± 0.18; stress: 2.24 ± 0.10 µmol glycerol/100 mg total lipids/100 min), epinephrine (control: 1.64 ± 0.17; stress: 2.24 ± 0.14 µmol glycerol/100 mg total lipids/100 min), salbutamol (control: 0.65 ± 0.11; stress: 1.21 ± 0.41 µmol glycerol/100 mg total lipids/100 min), and d-butyryl-cAMP (control: 1.59 ± 0.17; stress: 2.72 ± 0.25) were significantly enhanced in adipocytes from stressed rats. pD₂ or maximum response to CGP12177 were not altered. Supersensitivity to isoprenaline was abolished by 50 nM ICI118,551 but was not modified by 100 nM metoprolol. However, subsensitivity to norepinephrine and to BRL37344 was abolished by 100 nM metoprolol.

Our results suggest that in epididymal adipocytes from stressed rats there is a desensitization of the response to adrenoceptor agonists mediated by ß₁-adrenoceptors together with a sensitization of the response mediated by ß₂-adrenoceptors. ß₃-adrenoceptors seem to be resistant to the stress effect.—Farias-Silva, E., D. M. Grassi-Kassisse, V. Wolf-Nunes, and R. C. Spadari-Bratfisch. Stress-induced alteration in the lipolytic response to ß-adrenoceptor agonists in rat white adipocytes. J. Lipid Res. 1999. 40: 1719;–1727.

Supplementary key words: adrenergic receptors, footshock stress, epididymal adipocytes, sensitivity

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