title: α2C-Adrenoceptors modulate L-DOPA uptake in opossum kidney cells and in the mouse kidney.
abstract: Targeted deletion or selective pharmacological inhibition of α(2C)-adrenoceptors in mice results in increased brain tissue levels of dopamine and its precursor l-3,4-dihydroxyphenylalanine (l-DOPA), without significant changes in l-DOPA synthesis. l-DOPA uptake is considered the rate-limiting step in dopamine synthesis in the kidney. Since α(2C)-adrenoceptors may influence the transport of l-DOPA, we investigated the effect of α(2C)-adrenoceptor activation on l-DOPA uptake in a kidney cell line (opossum kidney cells). l-DOPA and dopamine kidney tissue levels in α(2C)-adrenoceptor knockout (α(2C)KO) mice and in mice treated with the selective α(2C)-adrenoceptor antagonist JP-1302 were also evaluated. The α(2)-adrenoceptor agonist medetomidine (0.1-1,000 nM) produced a concentration-dependent decrease in l-DOPA uptake in opossum kidney cells (IC(50): 2.5 ± 0.5 nM and maximal effect: 28 ± 5% of inhibition). This effect was abolished by a preincubation with JP-1302 (300 nM). Furthermore, the effect of medetomidine (100 nM) was abolished by a preincubation with U-0126 (10 μM), a MEK1/2 inhibitor. Kidney tissue levels of l-DOPA were significantly higher in α(2C)KO mice compared with wild-type mice (wild-type mice: 58 ± 2 pmol/g tissue and α(2C)KO mice: 81 ± 15 pmol/g tissue, P < 0.05) and in mice treated with JP-1302 (3 μmol/kg body wt) compared with control mice (control mice: 62 ± 2 pmol/g tissue and JP-1302-treated mice: 75 ± 1 pmol/g tissue, P < 0.05), both without significant changes in dopamine kidney tissue levels. However, mice treated with JP-1302 on a high-salt diet presented significantly higher dopamine levels in the kidney and urine compared with control animals on a high-salt diet. In conclusion, in a kidney cell line, α(2C)-adrenoceptor activation inhibits l-DOPA uptake, and in mice, deletion or blockade of α(2C)-adrenoceptors increases l-DOPA kidney tissue levels.
authors.affiliation: Departamento de Farmacologia e Terapêutica, Faculdade de Medicina, Universidade do Porto, Alameda Prof. Hernâni Monteiro, Porto 4200-319, Portugal. jedmoura@med.up.pt
authors.forename: Eduardo
authors.initials: E
authors.lastname: Moura
authors.forename: Elisabete
authors.initials: E
authors.lastname: Silva
authors.forename: Maria Paula
authors.initials: MP
authors.lastname: Serrão
authors.forename: Joana
authors.initials: J
authors.lastname: Afonso
authors.forename: Carina Esteves Pinto
authors.initials: CE
authors.lastname: Kozmus
authors.forename: Maria Augusta
authors.initials: MA
authors.lastname: Vieira-Coelho
mesh_terms: D000166:Acridines / Q000494:pharmacology; D058647:Adrenergic alpha-2 Receptor Agonists / Q000494:pharmacology; D058669:Adrenergic alpha-2 Receptor Antagonists / Q000494:pharmacology; D000818:Animals; D002460:Cell Line; D004298:Dopamine / Q000378:metabolism* / Q000652:urine; D015259:Dopamine Agents / Q000493:pharmacokinetics*; D004305:Dose-Response Relationship, Drug; D007668:Kidney / Q000187:drug effects / Q000378:metabolism*; D007980:Levodopa / Q000493:pharmacokinetics*; D048369:MAP Kinase Kinase 1 / Q000378:metabolism; D020926:Medetomidine / Q000494:pharmacology; D051379:Mice; D018345:Mice, Knockout; D009893:Opossums; D010879:Piperazines / Q000494:pharmacology; D018341:Receptors, Adrenergic, alpha-2 / Q000378:metabolism*; D015398:Signal Transduction / Q000187:drug effects / Q000502:physiology; D017673:Sodium Chloride, Dietary / Q000378:metabolism
chemical_list: D000166:Acridines; D058647:Adrenergic alpha-2 Receptor Agonists; D058669:Adrenergic alpha-2 Receptor Antagonists; D015259:Dopamine Agents; C518829:JP-1302; D010879:Piperazines; D018341:Receptors, Adrenergic, alpha-2; D017673:Sodium Chloride, Dietary; D007980:Levodopa; D048369:MAP Kinase Kinase 1; D020926:Medetomidine; D004298:Dopamine