title: The nitric oxide donor SIN-1 is free of tolerance and maintains its cyclic GMP stimulatory potency in nitrate-tolerant LLC-PK1 cells.
abstract: OBJECTIVE
  Using an established cell culture model, the present study investigates whether linsidomine (SIN-1), a spontaneous donor of nitric oxide and active metabolite of the antianginal drug molsidomine, induces tolerance to its own cyclic GMP stimulatory action or shows a diminished response after tolerance induction with glyceryl trinitrate.
  
  
  METHODS
  Incubations with nitric oxide donors were carried out in LLC-PK1 kidney epithelial cells. Intracellular levels of cyclic GMP, the vasodilatory second messenger of nitric oxide, were determined by radioimmunoassay.
  
  
  RESULTS
  A 5-h preincubation with glyceryl trinitrate (0.01-100 microM) led to complete inhibition of a subsequent cyclic GMP stimulation by glyceryl trinitrate but left the cyclic GMP response to SIN-1 unaltered. Similarly, cyclic GMP elevations by the spontaneous nitric oxide donors sodium nitroprusside and spermine NONOate were not affected after pretreatment with glyceryl trinitrate. Moreover, pretreatment with SIN-1 (1-1000 microM) had no significant effect on SIN-1-dependent cyclic GMP stimulation.
  
  
  CONCLUSIONS
  Our results show that in LLC-PK1 cells, SIN-1 is free of tolerance induction and not cross-tolerant to glyceryl trinitrate. This may be due to the spontaneous nitric oxide release from SIN-1, which in contrast to nitric acid esters does not require enzymatic bioactivation and may therefore be unaffected by nitrate tolerance.
authors.affiliation: Department of Pharmacology and Toxicology, School of Pharmacy, Martin Luther University Halle-Wittenberg, Halle (Saale), Germany.
authors.forename: B
authors.initials: B
authors.lastname: Hinz
authors.forename: H
authors.initials: H
authors.lastname: Schröder
mesh_terms: D000818:Animals; D006152:Cyclic GMP / Q000378:metabolism*; D004305:Dose-Response Relationship, Drug; D004361:Drug Tolerance; D006162:Guanylate Cyclase / Q000378:metabolism; D018374:LLC-PK1 Cells / Q000187:drug effects* / Q000201:enzymology; D008981:Molsidomine / Q000031:analogs & derivatives* / Q000494:pharmacology; D009153:Mutagens / Q000494:pharmacology; D009569:Nitric Oxide / Q000378:metabolism; D020030:Nitric Oxide Donors / Q000494:pharmacology*; D009589:Nitrogen Oxides; D005996:Nitroglycerin / Q000494:pharmacology*; D009599:Nitroprusside / Q000494:pharmacology; D013096:Spermine / Q000031:analogs & derivatives / Q000494:pharmacology; D013552:Swine; D014665:Vasodilator Agents / Q000494:pharmacology*
chemical_list: D009153:Mutagens; D020030:Nitric Oxide Donors; D009589:Nitrogen Oxides; D014665:Vasodilator Agents; C091861:spermine nitric oxide complex; D009599:Nitroprusside; D013096:Spermine; D009569:Nitric Oxide; C002385:linsidomine; D008981:Molsidomine; D006162:Guanylate Cyclase; D005996:Nitroglycerin; D006152:Cyclic GMP