title: Increased release of serotonin from rat ileum due to dexfenfluramine.
abstract: Plasma levels of serotonin are elevated in primary pulmonary hypertension even after bilateral lung transplantation, suggesting a possible etiologic role. Serotonin is released primarily from the small intestine. Anorectic agents, such as dexfenfluramine, which can cause pulmonary hypertension, are known to inhibit potassium channels in vascular smooth muscle cells. We examined the hypothesis that dexfenfluramine may stimulate release of serotonin from the ileum by inhibition of K+ channels. In an isolated loop of rat ileum perfused with a physiological salt solution, the administration of dexfenfluramine, its major metabolite D-norfenfluramine, the potassium channel blocker 4-aminopyridine (5 mM), and caffeine (30 mM) increased serotonin levels in the venous effluent. Potassium chloride (60 mM) tended to increase serotonin levels. In genetically susceptible individuals, dexfenfluramine may induce pulmonary hypertension by increasing cytosolic calcium in enterochromaffin cells of the small intestine, thus releasing serotonin and causing vasoconstriction. This work indicates that dexfenfluramine and its major metabolite d-norfenfluramine can increase serotonin release from the small intestine.
authors.affiliation: Department of Medicine, Veterans Administration Medical Center, University of Minnesota, Minneapolis 55417, USA. varghese@umn.edu
authors.forename: Shahrzad
authors.initials: S
authors.lastname: Rezaie-Majd
authors.forename: Jozef
authors.initials: J
authors.lastname: Murar
authors.forename: Daniel P
authors.initials: DP
authors.lastname: Nelson
authors.forename: Rosemary F
authors.initials: RF
authors.lastname: Kelly
authors.forename: Zhigang
authors.initials: Z
authors.lastname: Hong
authors.forename: Irene M
authors.initials: IM
authors.lastname: Lang
authors.forename: Anthony
authors.initials: A
authors.lastname: Varghese
authors.forename: E Kenneth
authors.initials: EK
authors.lastname: Weir
mesh_terms: D015761:4-Aminopyridine / Q000494:pharmacology; D000818:Animals; D002110:Caffeine / Q000494:pharmacology; D002118:Calcium / Q000378:metabolism; D002851:Chromatography, High Pressure Liquid; D003600:Cytosol / Q000187:drug effects / Q000378:metabolism; D020372:Dexfenfluramine / Q000494:pharmacology*; D005473:Fluoxetine / Q000494:pharmacology; D006976:Hypertension, Pulmonary / Q000503:physiopathology; D007082:Ileum / Q000187:drug effects / Q000378:metabolism*; D008297:Male; D026902:Potassium Channel Blockers / Q000494:pharmacology; D015221:Potassium Channels / Q000187:drug effects / Q000378:metabolism; D011189:Potassium Chloride / Q000494:pharmacology; D051381:Rats; D017207:Rats, Sprague-Dawley; D012701:Serotonin / Q000378:metabolism*; D017366:Serotonin Receptor Agonists / Q000494:pharmacology*; D017367:Selective Serotonin Reuptake Inhibitors / Q000494:pharmacology
chemical_list: D015761:4-Aminopyridine; D002110:Caffeine; D002118:Calcium; D020372:Dexfenfluramine; D005473:Fluoxetine; D026902:Potassium Channel Blockers; D015221:Potassium Channels; D011189:Potassium Chloride; D012701:Serotonin; D017366:Serotonin Receptor Agonists; D017367:Selective Serotonin Reuptake Inhibitors