Abstract
This study was undertaken in order to test the hypothesis that selective beta3-AR stimulation and simultaneous blockade of alpha2-AR would result in an increase of lipolysis and thermogenesis in rats. Incubation of isolated white adipocytes with the alpha2-AR antagonist yohimbine produced a concentration-dependent increase in glycerol release (P<0.001) for all assayed concentrations (10-12-10-6 M) and potentiated the lipolytic effect of the beta3-AR agonist Trecadrine. However, in vivo administration of yohimbine produced a marked decrease in body temperature (1.3-1.5 degrees C, P<0.001) and blocked the thermogenic effect of Trecadrine when simultaneously administered. A similar response was observed for whole body oxygen consumption. Furthermore, yohimbine did not modify brown adipose tissue oxygen consumption, but blocked the beta3-AR-mediated increase triggered by Trecadrine. Brown adipose tissue UCP-2 and -3 mRNA expression was not changed by yohimbine. In conclusion, the present work indicates that in vitro alpha2-AR blockade by yohimbine potentiates the beta3-AR-mediated stimulation of lipolysis. On the other hand, in vivo alpha2-AR antagonism blocks the thermogenic effects mediated by beta3-AR stimulation, suggesting a possible interplay between the receptors.
Publication types
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Research Support, Non-U.S. Gov't
MeSH terms
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Adipocytes / cytology
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Adipocytes / drug effects
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Adipocytes / metabolism
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Adipose Tissue, Brown / drug effects
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Adipose Tissue, Brown / metabolism
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Adrenergic alpha-2 Receptor Antagonists
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Adrenergic alpha-Antagonists / pharmacology*
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Adrenergic beta-3 Receptor Agonists
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Adrenergic beta-Agonists / pharmacology
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Animals
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Benzyl Alcohols / pharmacology
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Blood Glucose / drug effects
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Blood Glucose / metabolism
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Body Temperature / drug effects
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Carrier Proteins / genetics
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Dose-Response Relationship, Drug
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Drug Interactions
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Gene Expression Regulation / drug effects
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Glycerol / blood
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Insulin / blood
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Ion Channels
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Leptin / metabolism
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Lipolysis / drug effects*
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Male
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Membrane Proteins / genetics
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Mitochondrial Proteins
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Oxygen Consumption / drug effects
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RNA, Messenger / drug effects
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RNA, Messenger / genetics
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RNA, Messenger / metabolism
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Rats
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Rats, Wistar
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Rectum / physiology
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Thermogenesis / drug effects*
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Uncoupling Protein 1
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Yohimbine / pharmacology
Substances
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Adrenergic alpha-2 Receptor Antagonists
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Adrenergic alpha-Antagonists
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Adrenergic beta-3 Receptor Agonists
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Adrenergic beta-Agonists
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Benzyl Alcohols
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Blood Glucose
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Carrier Proteins
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Insulin
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Ion Channels
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Leptin
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Membrane Proteins
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Mitochondrial Proteins
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RNA, Messenger
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Uncoupling Protein 1
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Yohimbine
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trecadrine
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Glycerol