title: In situ studies of catecholamine-induced lipolysis in human adipose tissue using microdialysis.
abstract: The effects of catecholamines on lipolysis in situ were investigated in humans. Subcutaneous adipose tissue was microdialyzed with solvents containing adrenergic agents. Norepinephrine caused a rapid increase in the glycerol level in adipose tissue (lipolysis index) that was further increased by the alpha adrenoreceptor blocker phentolamine. At 10(-11) mol/l of norepinephrine caused a 100% stimulation of lipolysis (P less than .025). In the presence of phentolamine the lipolytic effects of catecholamines at 10(-12) mol/l was isoproterenol greater than epinephrine greater than norepinephrine. All these three lipolytic catecholamines caused a transient increase in the adipose tissue dialysate glycerol level, which peaked after 20 to 30 min of catecholamine exposure and then declined. The apparent tachyphylaxia could not be overcome by a gradual increase of the catecholamine concentration from 10(-12) to 10(-8) mol/l. However, the selective alpha-2 adrenoreceptor agonist clonidine caused a continuous and dose-dependent decrease in the dialysate glycerol level; the minimum effective concentration was 10(-9) mol/l. In conclusion, catecholamines have a lipolytic effect in situ at much lower concentrations than those in the circulation. This effect is transient and is related to beta adrenoreceptors. In additio, catecholamines have alpha adrenoreceptor-mediated effects on lipolysis in situ.
authors.affiliation: Department of Medicine, Huddinge Hospital, Sweden.
authors.forename: P
authors.initials: P
authors.lastname: Arner
authors.forename: E
authors.initials: E
authors.lastname: Kriegholm
authors.forename: P
authors.initials: P
authors.lastname: Engfeldt
mesh_terms: D000273:Adipose Tissue / Q000378:metabolism*; D002395:Catecholamines / Q000494:pharmacology*; D003956:Dialysis; D005260:Female; D005990:Glycerol / Q000032:analysis; D006801:Humans; D008066:Lipolysis / Q000187:drug effects*; D008297:Male; D011943:Receptors, Adrenergic, beta / Q000502:physiology; D013618:Tachyphylaxis
chemical_list: D002395:Catecholamines; D011943:Receptors, Adrenergic, beta; D005990:Glycerol