title: Role of cGMP-dependent protein kinase in development of tolerance to nitric oxide in pulmonary veins of newborn lambs.
abstract: Continuous exposure to nitrovasodilators and nitric oxide induces tolerance to their vasodilator effects in vascular smooth muscle. This study was done to determine the role of cGMP-dependent protein kinase (PKG) in the development of tolerance to nitric oxide. Isolated fourth-generation pulmonary veins of newborn lambs were studied. Incubation of veins for 20 h with DETA NONOate (DETA NO; a stable nitric oxide donor) significantly reduced their relaxation response to the nitric oxide donor and to beta-phenyl-1,N2-etheno-8-bromo-cGMP (8-Br-PET-cGMP, a cell-permeable cGMP analog). Incubation with DETA NO significantly reduced PKG activity and protein and mRNA levels in the vessels. These effects were prevented by 1H-(1,2,4)oxadiazolo(4,3-a)quinoxalin-1-one (an inhibitor of soluble guanylyl cyclase) and Rp-8-Br-PET-cGMPS (an inhibitor of PKG). A decrease in PKG protein and mRNA levels was also observed after continuous exposure to cGMP analogs. The PKG inhibitor abrogated these effects. The decrease in cGMP-mediated relaxation and in PKG activity caused by continuous exposure to DETA NO was not affected by KT-5720, an inhibitor of cAMP-dependent protein kinase. Prolonged exposure to 8-Br-cAMP (a cell-permeable cAMP analog) did not affect PKG protein level in the veins. These results suggest that continuous exposure to nitric oxide or cGMP downregulates PKG by a PKG-dependent mechanism. Such a negative feedback mechanism may contribute to the development of tolerance to nitric oxide in pulmonary veins of newborn lambs.
authors.affiliation: Harbor-UCLA Medical Center, Research and Education Institute, 1124 W. Carson St., RB-1, Torrance, CA 90502, USA. ygao@gcrc.rei.edu
authors.forename: Yuansheng
authors.initials: Y
authors.lastname: Gao
authors.forename: Srinivas
authors.initials: S
authors.lastname: Dhanakoti
authors.forename: Earleen M
authors.initials: EM
authors.lastname: Trevino
authors.forename: Xiaohua
authors.initials: X
authors.lastname: Wang
authors.forename: Fred C
authors.initials: FC
authors.lastname: Sander
authors.forename: Ada D
authors.initials: AD
authors.lastname: Portugal
authors.forename: J Usha
authors.initials: JU
authors.lastname: Raj
mesh_terms: D000818:Animals; D000831:Animals, Newborn; D006152:Cyclic GMP / Q000031:analogs & derivatives* / Q000378:metabolism* / Q000494:pharmacology; D017869:Cyclic GMP-Dependent Protein Kinases / Q000235:genetics / Q000378:metabolism*; D004789:Enzyme Activation / Q000187:drug effects / Q000502:physiology; D025461:Feedback, Physiological; D005260:Female; D008297:Male; D009569:Nitric Oxide / Q000378:metabolism*; D020030:Nitric Oxide Donors / Q000494:pharmacology; D009603:Nitroso Compounds / Q000494:pharmacology; D009924:Organ Culture Techniques; D011667:Pulmonary Veins / Q000187:drug effects / Q000201:enzymology*; D012333:RNA, Messenger / Q000032:analysis; D012756:Sheep
chemical_list: C104224:8-bromo-beta-phenylethenoguanosine 3',5'-cyclic monophosphate; D020030:Nitric Oxide Donors; D009603:Nitroso Compounds; D012333:RNA, Messenger; C094210:2,2'-(hydroxynitrosohydrazono)bis-ethanamine; D009569:Nitric Oxide; D017869:Cyclic GMP-Dependent Protein Kinases; D006152:Cyclic GMP