title: Ephedrine, a potential slimming drug, directly stimulates thermogenesis in brown adipocytes via beta-adrenoreceptors.
abstract: Ephedrine is a potential slimming drug that stimulates thermogenesis in man and laboratory animals. Considering that brown adipose tissue is an important site of catecholamine-induced thermogenesis in homeotherms, we tested the thermogenic efficiency of several ephedrine stereoisomers on adipocytes isolated from rat interscapular brown adipose tissue. Addition of (-)-ephedrine (0.1 mM) to brown adipocyte suspensions rapidly stimulated cellular respiration eight times above basal values. A stable Vmax of 335 nmol O2/min/10(6) cells was reached less than 5 min after the onset of respiratory stimulation. This value represents 85 percent of the maximal respiration observed with norepinephrine, the physiological effector of thermogenesis. The (-)isomer of ephedrine (1/2 Vmax = 20 microM) was more potent that other stereoisomers (+)-psi-ephedrine, (-)-psi-ephedrine (racephedrine) in enhancing brown adipocyte respiration. Beta-Adrenergic antagonists (alprenolol and propranolol) were much more effective than alpha-adrenergic antagonists (phentolamine and phenoxybenzamine) in inhibiting the respiratory effects of ephedrine. It is concluded that (-)-ephedrine mimics the calorigenic action of norepinephrine by directly stimulating brown adipocyte respiration via beta-adrenoreceptors.
mesh_terms: D002001:Adipose Tissue, Brown / Q000166:cytology / Q000502:physiology*; D000818:Animals; D001833:Body Temperature Regulation / Q000187:drug effects*; D002478:Cells, Cultured; D004305:Dose-Response Relationship, Drug; D004809:Ephedrine / Q000494:pharmacology*; D005260:Female; D009638:Norepinephrine / Q000494:pharmacology; D009765:Obesity / Q000188:drug therapy; D010101:Oxygen Consumption / Q000187:drug effects*; D011433:Propranolol / Q000494:pharmacology; D051381:Rats; D011919:Rats, Inbred Strains; D011941:Receptors, Adrenergic / Q000502:physiology*; D011942:Receptors, Adrenergic, alpha / Q000502:physiology; D011943:Receptors, Adrenergic, beta / Q000502:physiology*; D013237:Stereoisomerism; D013268:Stimulation, Chemical
chemical_list: D011941:Receptors, Adrenergic; D011942:Receptors, Adrenergic, alpha; D011943:Receptors, Adrenergic, beta; D011433:Propranolol; D004809:Ephedrine; D009638:Norepinephrine