Chronic hypoxia attenuates cGMP-dependent pulmonary vasodilation.
Chronic hypoxia (CH) augments endothelium-derived nitric oxide (NO)-dependent pulmonary vasodilation; however, responses to exogenous NO are reduced following CH in female rats. We hypothesized that CH-induced attenuation of NO-dependent pulmonary vasodilation is mediated by downregulation of vascular smooth muscle (VSM) soluble guanylyl cyclase (sGC) expression and/or activity, increased cGMP degradation by phosphodiesterase type 5 (PDE5), or decreased VSM sensitivity to cGMP. Experiments demonstrated attenuated vasodilatory responsiveness to the NO donors S-nitroso-N-acetylpenicillamine and spermine NONOate and to arterial boluses of dissolved NO solutions in isolated, saline-perfused lungs from CH vs. normoxic female rats. In additional experiments, the sGC inhibitor, 1H-[1,2,4]oxadiazolo[4,3-a]quinoxalin-1-one, blocked vasodilation to NO donors in lungs from each group. However, CH was not associated with decreased pulmonary sGC expression or activity as assessed by Western blotting and cGMP radioimmunoassay, respectively. Consistent with our hypothesis, the selective PDE5 inhibitors dipyridamole and T-1032 augmented NO-dependent reactivity in lungs from CH rats, while having little effect in lungs from normoxic rats. However, the attenuated vasodilatory response to NO in CH lungs persisted after PDE5 inhibition. Furthermore, CH similarly inhibited vasodilatory responses to 8-bromoguanosine 3'5'-cyclic monophosphate. We conclude that attenuated NO-dependent pulmonary vasodilation after CH is not likely mediated by decreased sGC expression, but rather by increased cGMP degradation by PDE5 and decreased pulmonary VSM reactivity to cGMP.
Jernigan
Nikki L
NL
Vascular Physiology Group, Department of Cell Biology and Physiology, University of New Mexico Health Sciences Center, Albuquerque, New Mexico 87131-5218, USA. njernigan@salud.unm.edu
Resta
Thomas C
TC
D015106:3',5'-Cyclic-GMP Phosphodiesterases / Q000037:antagonists & inhibitors; D000818:Animals; D015153:Blotting, Western; D002908:Chronic Disease; D006152:Cyclic GMP / Q000031:analogs & derivatives* / Q000378:metabolism* / Q000494:pharmacology; D054706:Cyclic Nucleotide Phosphodiesterases, Type 5; D004791:Enzyme Inhibitors / Q000494:pharmacology; D005260:Female; D006162:Guanylate Cyclase; D017380:Hypertrophy, Right Ventricular / Q000209:etiology / Q000503:physiopathology; D000860:Hypoxia / Q000150:complications / Q000503:physiopathology*; D066298:In Vitro Techniques; D008168:Lung / Q000098:blood supply* / Q000378:metabolism; D009131:Muscle, Smooth, Vascular / Q000187:drug effects / Q000378:metabolism*; D009569:Nitric Oxide / Q000494:pharmacology; D020030:Nitric Oxide Donors / Q000494:pharmacology; D019335:Nitroarginine / Q000494:pharmacology; D011086:Polycythemia / Q000209:etiology; D011863:Radioimmunoassay; D051381:Rats; D017207:Rats, Sprague-Dawley; D018160:Receptors, Cytoplasmic and Nuclear / Q000037:antagonists & inhibitors; D000071756:Soluble Guanylyl Cyclase; D014664:Vasodilation / Q000187:drug effects
D004791:Enzyme Inhibitors; D020030:Nitric Oxide Donors; D018160:Receptors, Cytoplasmic and Nuclear; D019335:Nitroarginine; C016276:8-bromocyclic GMP; D009569:Nitric Oxide; D015106:3',5'-Cyclic-GMP Phosphodiesterases; D054706:Cyclic Nucleotide Phosphodiesterases, Type 5; C517384:Pde5a protein, rat; D006162:Guanylate Cyclase; D000071756:Soluble Guanylyl Cyclase; D006152:Cyclic GMP