title: Lack of effect of ODQ does not exclude cGMP signalling via NO-sensitive guanylyl cyclase.
abstract: OBJECTIVE
  Nitric oxide (NO) is known to activate NO-sensitive guanylyl cyclase (NO-GC) and to elicit cGMP production. However, NO has also been proposed to induce cGMP-independent effects. It is accepted practice to use specific NO-GC inhibitors, such as ODQ or NS2028, to assess cGMP-dependent NO effects. Consequently, NO-induced reactions seen in the presence of these inhibitors commonly serve as an affirmation of cGMP independence.
  
  
  METHODS
  We evaluated the use of ODQ to discriminate between cGMP-dependent and cGMP-independent NO effects. NO-GC-expressing HEK cells, platelets and tissues from wild type (WT) and NO-GC-deficient mice (GCKO) were used.
  
  
  RESULTS
  NO donors led to accumulation of cGMP in platelets and GC-expressing HEK cells and induced phosphorylation of the vasodilator-stimulated phosphoprotein in platelets; both effects were reduced by ODQ. High concentrations of NO donors, however, overrode the inhibitory effect of ODQ. Correspondingly, ODQ inhibited but did not fully eliminate NO-induced relaxation of aorta and fundus from WT mice. Relaxation induced by endogenously released NO was fully or partially inhibited by ODQ in fundus and aorta, respectively. In aorta and fundus of GCKO mice NO-induced relaxation was absent and served as standard for complete NO-GC inhibition.
  
  
  CONCLUSIONS
  High NO concentrations can overcome the inhibitory effect of ODQ on NO-GC. Smooth muscle relaxation induced by NO donors/endogenously released NO in the presence of ODQ in WT was absent in GCKO animals indicating involvement of NO-GC. Accordingly, NO-induced effects in the presence of ODQ do not necessarily prove cGMP independence.
authors.affiliation: Institute of Physiology, University of Würzburg, Würzburg, Germany.
authors.forename: Barbara
authors.initials: B
authors.lastname: Lies
authors.forename: Dieter
authors.initials: D
authors.lastname: Groneberg
authors.forename: Stepan
authors.initials: S
authors.lastname: Gambaryan
authors.forename: Andreas
authors.initials: A
authors.lastname: Friebe
mesh_terms: D000328:Adult; D000818:Animals; D001011:Aorta / Q000187:drug effects / Q000378:metabolism; D006152:Cyclic GMP / Q000378:metabolism*; D005260:Female; D006162:Guanylate Cyclase / Q000235:genetics / Q000378:metabolism*; D057809:HEK293 Cells; D006801:Humans; D008297:Male; D051379:Mice; D008810:Mice, Inbred C57BL; D018345:Mice, Knockout; D009126:Muscle Relaxation / Q000187:drug effects / Q000502:physiology; D009130:Muscle, Smooth / Q000187:drug effects / Q000378:metabolism; D009569:Nitric Oxide / Q000378:metabolism*; D020030:Nitric Oxide Donors / Q000494:pharmacology; D010069:Oxadiazoles / Q000494:pharmacology*; D010078:Oxazines / Q000494:pharmacology; D015398:Signal Transduction / Q000187:drug effects / Q000502:physiology
chemical_list: C116907:1H-(1,2,4)oxadiazolo(4,3-a)-quiloxalin-1-one; C111257:NS 2028; D020030:Nitric Oxide Donors; D010069:Oxadiazoles; D010078:Oxazines; D009569:Nitric Oxide; D006162:Guanylate Cyclase; D006152:Cyclic GMP
keywords: NO-sensitive guanylyl cyclase; ODQ; VASP; cGMP; cGMP-independent effects; knockout mice; nitric oxide; platelet; signal transduction