title: Protein kinase G is not essential to NO-cGMP modulation of basal tone in rat pulmonary circulation.
abstract: Nitric oxide (NO) is important in modulating increased pulmonary vascular tone. Whereas in other systems it is believed that the action of NO is mediated through guanosine 3',5'-cyclic monophosphate (cGMP) and protein kinase G (PKG), the validity of this pathway in the pulmonary circulation has not been established. Using isolated salt-perfused normotensive and hypertensive rat lungs, we studied the effects of the soluble guanylyl cyclase inhibitor, 1H-[1,2,4]oxadiazolo[4,3-a]quinoxalin-1-one (ODQ), and the PKG inhibitors, KT5823, Rp-8-pCPT-cGMPS, and (N-[2-(methylamino)ethyl]-5-isoquinolinesulfonamide) (H-8), on pulmonary vascular resistance. In isolated normotensive lungs, ODQ-mediated inhibition of soluble guanylyl cyclase augmented hypoxic pulmonary vasoconstriction, whereas the PKG inhibitors had no effect. Despite the marked differences in the physiological effect, ODQ and Rp-8-pCPT-cGMPS inhibited PKG activity to a similar degree as determined by a back-phosphorylation assay showing decreased PKG-mediated phosphorylation of serine 1755 on the D-myo-inositol 1,4,5-trisphosphate receptor. In hypertensive lungs, inhibition of soluble guanylyl cyclase by ODQ increased perfusion pressure by 101 +/- 20% (P < 0.05), an increase similar to that seen with inhibition of NO synthase (NOS), confirming an essential role for cGMP. In contrast, KT5823, Rp-8-pCPT-cGMPS, and H-8 (used in doses 5- to 100-fold in excess of their reported inhibitory concentrations for PKG) caused only a small increase in baseline perfusion pressure (14 +/- 2%, P = not significant from vehicle control). Effectiveness of PKG inhibition in the hypertensive lungs was also confirmed with the back-phosphorylation assay. These studies suggest that whereas NO-mediated modulation of vascular tone in the normotensive and hypertensive pulmonary circulation is dependent on cGMP formation, activation of PKG may not be essential.
authors.affiliation: Division of Pulmonary Sciences, University of Colorado Health Sciences Center, Denver 80262-0001, USA.
authors.forename: B
authors.initials: B
authors.lastname: Fouty
authors.forename: P
authors.initials: P
authors.lastname: Komalavilas
authors.forename: M
authors.initials: M
authors.lastname: Muramatsu
authors.forename: A
authors.initials: A
authors.lastname: Cohen
authors.forename: I F
authors.initials: IF
authors.lastname: McMurtry
authors.forename: T M
authors.initials: TM
authors.lastname: Lincoln
authors.forename: D M
authors.initials: DM
authors.lastname: Rodman
mesh_terms: D000470:Alkaloids / Q000494:pharmacology; D000818:Animals; D001794:Blood Pressure / Q000187:drug effects; D002227:Carbazoles; D006152:Cyclic GMP / Q000031:analogs & derivatives / Q000494:pharmacology*; D004791:Enzyme Inhibitors / Q000494:pharmacology; D006162:Guanylate Cyclase / Q000037:antagonists & inhibitors; D006976:Hypertension, Pulmonary / Q000503:physiopathology*; D007211:Indoles; D008168:Lung / Q000098:blood supply; D008297:Male; D009569:Nitric Oxide / Q000494:pharmacology*; D010069:Oxadiazoles / Q000494:pharmacology; D047428:Protein Kinase Inhibitors; D011494:Protein Kinases / Q000502:physiology*; D011652:Pulmonary Circulation / Q000187:drug effects*; D011810:Quinoxalines / Q000494:pharmacology; D051381:Rats; D017207:Rats, Sprague-Dawley; D013873:Thionucleotides / Q000494:pharmacology; D014655:Vascular Resistance / Q000187:drug effects; D014661:Vasoconstriction / Q000187:drug effects
chemical_list: C095284:1H-(1,2,4)oxadiazolo(4,3-a)quinoxalin-1-one; C090860:8-(4-chlorophenylthio)guanosine 3',5'-cyclic monophosphorothioate; D000470:Alkaloids; D002227:Carbazoles; D004791:Enzyme Inhibitors; D007211:Indoles; D010069:Oxadiazoles; D047428:Protein Kinase Inhibitors; D011810:Quinoxalines; D013873:Thionucleotides; C073601:KT 5823; D009569:Nitric Oxide; D011494:Protein Kinases; D006162:Guanylate Cyclase; D006152:Cyclic GMP