title: D1-like dopamine receptor activation and natriuresis by nitrocatechol COMT inhibitors.
abstract: BACKGROUND
  In recent years, several nitrocatechol derivatives (tolcapone, entacapone, and nitecapone) have been developed and found to be highly selective and potent inhibitors of catechol-O-methyltransferase (COMT). More recently, natriuretic properties were described for two of these compounds (entacapone and nitecapone), although this was not accompanied by enhanced urinary excretion of dopamine. We hypothesized that nitrocatechol derivatives stimulate D1-like dopamine receptors.
  
  
  METHODS
  Adult male Wistar rats were treated with a nitrocatechol COMT inhibitor (entacapone, tolcapone, or nitecapone, 30 mg/kg, orally), and the urinary excretion of dopamine and sodium was quantitated. The interaction of nitrocatechol derivatives with D1-like receptors was evaluated by their ability to displace [3H]-Sch23390 binding from membranes of rat renal cortex and cAMP production in opossum kidney (OK) cells.
  
  
  RESULTS
  Urinary excretion of sodium (micromol/h) was markedly increased by all three nitrocatechol derivatives: vehicle, 55.0 +/- 5.6; entacapone, 98.4 +/- 9.3; tolcapone, 97.5 +/- 9.3; and nitecapone, 120.5 +/- 12.6. Pretreatment with the selective D1 antagonist Sch 23390 (60 microg/kg) completely prevented their natriuretic effects. Nitecapone and tolcapone were equipotent (IC50s of 48 and 42 micromol/L) and more potent than entacapone and dopamine (IC50s of 107 and 279 micromol/L) in displacing [3H]-Sch23390 binding. In OK cells, all three nitrocatechol derivatives significantly increased cAMP accumulation and reduced Na(+)/H(+) exchange and Na(+),K(+)-ATPase activities, this being prevented by a blockade of D1-like receptors.
  
  
  CONCLUSIONS
  Stimulation of D1-like dopamine receptors and inhibition of Na(+)/H(+) exchange and Na(+),K(+)-ATPase activities by nitrocatechol COMT inhibitors may contribute to natriuresis produced by these compounds.
authors.affiliation: Institute of Pharmacology and Therapeutics, Faculty of Medicine, Porto, Portugal.
authors.forename: M A
authors.initials: MA
authors.lastname: Vieira-Coelho
authors.forename: P
authors.initials: P
authors.lastname: Gomes
authors.forename: M P
authors.initials: MP
authors.lastname: Serrão
authors.forename: P
authors.initials: P
authors.lastname: Soares-da-Silva
mesh_terms: D000818:Animals; D001552:Benzazepines / Q000378:metabolism; D001577:Benzophenones / Q000378:metabolism / Q000494:pharmacology; D001667:Binding, Competitive; D065098:Catechol O-Methyltransferase Inhibitors; D002396:Catechols / Q000378:metabolism / Q000494:pharmacology*; D002460:Cell Line; D000242:Cyclic AMP / Q000096:biosynthesis; D004791:Enzyme Inhibitors / Q000378:metabolism / Q000494:pharmacology*; D066298:In Vitro Techniques; D017136:Ion Transport; D007672:Kidney Cortex / Q000378:metabolism; D008297:Male; D009318:Natriuresis / Q000187:drug effects*; D009570:Nitriles; D009596:Nitrophenols; D009893:Opossums; D010422:Pentanones / Q000378:metabolism / Q000494:pharmacology; D051381:Rats; D017208:Rats, Wistar; D017447:Receptors, Dopamine D1 / Q000187:drug effects* / Q000378:metabolism*; D000254:Sodium-Potassium-Exchanging ATPase / Q000037:antagonists & inhibitors; D000077867:Tolcapone
chemical_list: D001552:Benzazepines; D001577:Benzophenones; D065098:Catechol O-Methyltransferase Inhibitors; D002396:Catechols; D004791:Enzyme Inhibitors; D009570:Nitriles; D009596:Nitrophenols; D010422:Pentanones; D017447:Receptors, Dopamine D1; C071192:entacapone; C057364:nitecapone; D000077867:Tolcapone; D000242:Cyclic AMP; D000254:Sodium-Potassium-Exchanging ATPase