Effect of aging on norepinephrine and phenylephrine stimulated lactate production by white adipocytes.
We have recently demonstrated that adipose tissue can produce lactate independently of lipolysis in insulin-resistant rats and that lactate production depends on alpha 1-adrenergic stimulation. In this study, we have investigated the influence of aging on norepinephrine-and-phenylephrine-stimulated lactate production and glycerol production. We showed that basal and norepinephrine stimulated lactate production were significantly increased in adipocytes isolated from old vs. young rats (0.165 +/- 0.006 vs. 0.055 +/- 0.008 for basal and 0.567 +/- 0.026 vs. 0.277 +/- 0.019 mumol lactate/10(6) cells/15 minutes for norepinephrine-stimulated lactate production, respectively, p < 0.05). The sensitivity of lactate production to norepinephrine stimulation in adipocytes isolated from old rats was significantly decreased (EC50 = 523 +/- 63.7 vs. 46.7 +/- 6.34 nM, respectively, p < 0.05). Maximal lactate production obtained with norepinephrine and phenylephrine was not significantly different in either group (0.567 +/- 0.026 vs. 0.520 +/- 0.036 in old and 0.277 +/9 0.019 vs. 0 275 +/- 0.017 mumol/10(6) cell/15 minutes in young rats, respectively, ns). Lactate production by adipocytes isolated from old rats were significantly less sensitive to phenylephrine stimulation compared with young (EC50 = 3.67 +/- 1.16 vs. 0.07 +/- 0.01 nM, respectively, p < 0.05) indicating that the effects of aging on norepinephrine and phenylephrine stimulation were probably induced by a decreased number of alpha 1-adrenoceptors. The mechanism by which aging increases adipocyte responsiveness of lactate production has not yet been elucidated.
Faintrenie
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G
UMR 5578-CNRS, Laboratoire de Physiologie des Régulations Energétiques, Cellulaires et Moléculaires, Lyon, France.
Géloën
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A
D017667:Adipocytes / Q000166:cytology / Q000378:metabolism* / Q000502:physiology; D000375:Aging / Q000378:metabolism* / Q000502:physiology; D000704:Analysis of Variance; D000818:Animals; D002478:Cells, Cultured; D004305:Dose-Response Relationship, Drug; D005947:Glucose / Q000378:metabolism; D005990:Glycerol / Q000378:metabolism; D007773:Lactates / Q000378:metabolism*; D008066:Lipolysis / Q000187:drug effects; D008297:Male; D018377:Neurotransmitter Agents / Q000494:pharmacology; D009638:Norepinephrine / Q000494:pharmacology*; D010656:Phenylephrine / Q000494:pharmacology*; D051381:Rats; D017207:Rats, Sprague-Dawley; D018340:Receptors, Adrenergic, alpha-1 / Q000032:analysis / Q000502:physiology; D014662:Vasoconstrictor Agents / Q000494:pharmacology
D007773:Lactates; D018377:Neurotransmitter Agents; D018340:Receptors, Adrenergic, alpha-1; D014662:Vasoconstrictor Agents; D010656:Phenylephrine; D005947:Glucose; D005990:Glycerol; D009638:Norepinephrine