title: [3H]Tyramine uptake by rat liver slices.
abstract: Rat liver slices were employed as experimental model to characterise the system involved in the transport process which participates in liver tyramine uptake. The uptake of 0.4 micromol l-1of [3H]tyramine by rat liver slices was linear from 5 min up to the end of incubation. At 15 min the uptake was 4.58+/-0.18 pmol mg-1protein. The accumulation of [3H]tyramine was sensitive to temperature (69. 3+/-4.0% inhibition at 0 degrees C, P<0.001), to sodium omission replaced by 150 mmol l-1Tris or 110 mmol l-1Tris+40 mmol l-1choline (27.6+/-6.0%, P<0.01, and 24.6+/-3.8% inhibition, P<0.01, respectively), and the inhibition of Na+-K+-adenosine triphosphatase by 150 micromol l-1ouabain (20.4+/-2.6% decrease, P<0.01). Uptake of [3H]tyramine was cocaine- (10 micromol l-1) and desipramine- (1 micromol l-1) dependent (32.2+/-6.4%, P<0.05, and 31.6+/-4.0% inhibition, P<0.05, respectively). Uptake of [3H]tyramine in rat liver slices was not modified by 30 micromol l-1isoprenaline, 30 micromol l-1corticosterone, 30 micromol l-1normetanephrine and noradrenaline up to 4 micrometers at higher noradrenaline concentrations tyramine transport was diminished (P<0.05). Results achieved by incubation with increasing tyramine concentrations indicate that at the micromolar level hepatic uptake occurs by a combined passive diffusion and transport-mediated mechanism, whereas at greater tyramine concentrations passive transport predominates. These results suggest that both simple diffusion and a transport-mediated mechanism are involved in this uptake from hepatocytes, which presents features similar to those described for type 1 non-neuronal uptake systems.
authors.affiliation: Cátedra de Farmacologiá, Facultad de Farmacia y Bioquímica, Universidad de Buenos Aires, Junín 956, Buenos Aires, Argentina.
authors.forename: D M
authors.initials: DM
authors.lastname: Tchercansky
authors.forename: M C
authors.initials: MC
authors.lastname: Rubio
authors.forename: C
authors.initials: C
authors.lastname: Acevedo
mesh_terms: D000305:Adrenal Cortex Hormones / Q000494:pharmacology; D018759:Adrenergic Uptake Inhibitors; D000818:Animals; D002470:Cell Survival / Q000187:drug effects; D003042:Cocaine / Q000494:pharmacology; D003891:Desipramine / Q000494:pharmacology; D018765:Dopamine Uptake Inhibitors / Q000494:pharmacology; D004305:Dose-Response Relationship, Drug; D066298:In Vitro Techniques; D007545:Isoproterenol / Q000494:pharmacology; D008099:Liver / Q000166:cytology / Q000187:drug effects / Q000378:metabolism*; D008297:Male; D009638:Norepinephrine / Q000493:pharmacokinetics; D009647:Normetanephrine / Q000494:pharmacology; D051381:Rats; D017208:Rats, Wistar; D012964:Sodium / Q000494:pharmacology; D013566:Sympathomimetics / Q000493:pharmacokinetics*; D013696:Temperature; D013997:Time Factors; D014316:Tritium; D014439:Tyramine / Q000493:pharmacokinetics*
chemical_list: D000305:Adrenal Cortex Hormones; D018759:Adrenergic Uptake Inhibitors; D018765:Dopamine Uptake Inhibitors; D013566:Sympathomimetics; D009647:Normetanephrine; D014316:Tritium; D012964:Sodium; D003042:Cocaine; D007545:Isoproterenol; D003891:Desipramine; D009638:Norepinephrine; D014439:Tyramine