Role of cGMP-dependent protein kinase in development of tolerance to nitric oxide in pulmonary veins of newborn lambs.
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.
Gao
Yuansheng
Y
Harbor-UCLA Medical Center, Research and Education Institute, 1124 W. Carson St., RB-1, Torrance, CA 90502, USA. ygao@gcrc.rei.edu
Dhanakoti
Srinivas
S
Trevino
Earleen M
EM
Wang
Xiaohua
X
Sander
Fred C
FC
Portugal
Ada D
AD
Raj
J Usha
JU
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
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