title: Characterization of lipolytic responses of isolated white adipocytes from hamsters.
abstract: 1. Lipolysis by isolated white adipocytes from hamsters, as measured by glycerol production, was stimulated by corticotropin, isopropylnorepinephrine (INE), norepinephrine, or epinephrine (EPI), in a dose-dependent fashion. 2. Lipolysis was stimulated by five inhibitors of cyclic 3',5'-adenosine monophosphate phosphodiesterase: caffeine, theophylline, 1-methyl-3-isobutyl xanthine, 1-ethyl-4-(isopropylidenehydrazine)-1H-pyrazolo-(3,4,-b)-pyridine-5-carboxylic acid ethyl ester (SQ 20009), and 4-(3,4-dimethoxybenzyl)-2-imidazolidinone (Ro 7-2956). Caffeine-stimulated lipolysis consistently attained higher rates than did hormone-stimulated lipolysis. However, when cells were stimulated by both caffeine and a hormone, lipolytic rates were consistently lower than those attained under the influence of caffeine alone. 3. Isolated white adipocytes from hamsters were sensitive to both alpha- and beta-adrenergic antagonists. The beta-adrenergic antagonist propranolol could completely inhibit norepinephrine-stimulated glycerol production. The alpha-adrenergic antagonist phentolamine, on the other hand, had a biphasic effect on the cells. At 5-10(-7) M or 5-10(-6) M, phentolamine enhanced norepinephrine-stimulated lipolysis, while concentrations higher than 5-10(-5) M caused inhibition. 4. The effects of two different concentrations of six antilipolytic agents, prostaglandin E1, nicotinic acid, phenylisopropyladenosine, 5-methylpyrazole-3-carboxylic acid, adenosine and insulin, were measured. With the exception of insulin, all of these agents showed much more potent inhibition of caffeine-stimulated lipolysis than of hormone-stimulated lipolysis. Insulin, in contrast, showed only modest inhibition of hormone-stimulated lipolysis and virtually no inhibition of caffeine-stimulated lipolysis.
mesh_terms: D000241:Adenosine / Q000494:pharmacology; D000273:Adipose Tissue / Q000166:cytology / Q000378:metabolism*; D000324:Adrenocorticotropic Hormone / Q000494:pharmacology; D000818:Animals; D002110:Caffeine / Q000494:pharmacology; D002395:Catecholamines / Q000494:pharmacology; D006224:Cricetinae; D004305:Dose-Response Relationship, Drug; D005990:Glycerol / Q000378:metabolism; D007328:Insulin / Q000494:pharmacology; D008053:Lipid Mobilization / Q000187:drug effects; D008297:Male; D009539:Nicotinic Acids / Q000494:pharmacology; D009638:Norepinephrine / Q000494:pharmacology; D010646:Phentolamine / Q000494:pharmacology; D011433:Propranolol / Q000494:pharmacology; D011458:Prostaglandins E / Q000494:pharmacology
chemical_list: D002395:Catecholamines; D007328:Insulin; D009539:Nicotinic Acids; D011458:Prostaglandins E; D002110:Caffeine; D000324:Adrenocorticotropic Hormone; D011433:Propranolol; D000241:Adenosine; D005990:Glycerol; D009638:Norepinephrine; D010646:Phentolamine