title: Effect of phenylephrine on lipolysis in rat adipocytes: no evidence for an alpha-adrenergic mechanism.
abstract: Phenylephrine, a strong alpha 1-adrenergic agonist, exerted a concentration dependent antilipolytic effect against isoproterenol-activated lipolysis in rat adipocytes with the effect decreasing as the isoproterenol concentration increased. The alpha-adrenergic antagonists phentolamine and phenoxybenzamine did not reverse phenylephrine's antilipolytic effect. Phenylephrine alone activated lipolysis at concentrations above 10(-5) M and at 5 X 10(-4) M the rate of lipolysis was increased 3.4-fold. Propranolol abolished this effect. In the presence of sub-maximum concentrations of dibutyryl cyclic-AMP (less than 10(-4) M), 10(-4) M phenylephrine increased the rate of lipolysis above that activated by dibutyryl cyclic-AMP alone. At maximum dibutyryl cyclic-AMP concentrations, or in the presence of propranolol, phenylephrine had no effect on dibutyryl cyclic-AMP-dependent lipolysis. There is no evidence to support an alpha 1-adrenergic mechanism for regulation of lipolysis in the rat adipocyte. All effects of the alpha-adrenergic agonist phenylephrine appear to be due to its weak beta-adrenergic activity.
mesh_terms: D000273:Adipose Tissue / Q000187:drug effects* / Q000378:metabolism; D000818:Animals; D003994:Bucladesine / Q000494:pharmacology; D066298:In Vitro Techniques; D007545:Isoproterenol / Q000494:pharmacology; D008066:Lipolysis / Q000187:drug effects*; D008297:Male; D010656:Phenylephrine / Q000494:pharmacology*; D051381:Rats; D011919:Rats, Inbred Strains; D011942:Receptors, Adrenergic, alpha / Q000187:drug effects / Q000378:metabolism*
chemical_list: D011942:Receptors, Adrenergic, alpha; D010656:Phenylephrine; D003994:Bucladesine; D007545:Isoproterenol