title: Hypoxic depression of PKG-mediated inhibition of serotonergic contraction in ovine carotid arteries.
abstract: Chronic hypoxia attenuates soluble guanylate cyclase-induced vasorelaxation in serotonin (5-HT)-contracted ovine carotid arteries. Because protein kinase G (PKG) mediates many effects of soluble guanylate cyclase activation through phosphorylation of multiple kinase targets in vascular smooth muscle, we tested the hypothesis that chronic hypoxia reduces the ability of PKG to phosphorylate its target proteins, which attenuates the ability of PKG to induce vasorelaxation. We also tested the hypothesis that hypoxia attenuates PKG expression and/or activity. Arteries from normoxic and chronically hypoxic (altitude of 3,820 m for 110 days) fetal and adult sheep were denuded of endothelium and equilibrated with 95% O2-5% CO2 in the presence of nitro-l-arginine methyl ester (l-NAME) and N(G)-nitro-l-arginine (l-NNA) to inhibit residual endothelial nitric oxide synthase. Concentration-response relations for 5-HT were determined in the presence of prazosin to minimize activation of α-adrenergic receptors. The PKG activator 8-(p-chlorophenylthio)-guanosine 3',5'-cyclic monophosphate (8-pCTP-cGMP) reduced agonist binding affinity of the 5-HT receptor in a concentration-dependent manner that was attenuated by hypoxia. Expression and activity of PKG-I was not significantly affected by chronic hypoxia in either fetal or adult arteries, although PKG-I abundance was greater in fetal arteries. Pretreatment with the large conductance calcium-sensitive potassium channel (BK) inhibitor iberiotoxin attenuated the vasorelaxation induced by 8-pCPT-cGMP in normoxic but not chronically hypoxic arteries. These results support the hypothesis that hypoxia attenuates the vasorelaxant effects of PKG through suppression of the ability of PKG to activate large conductance calcium-sensitive potassium channels in arterial smooth muscle. The results also reveal that this hypoxic effect is greater in fetal than adult arteries and that chronic maternal hypoxia can profoundly affect fetal vascular function.
authors: Divisions of Physiology, Pharmacology, and Biochemistry, Center for Perinatal Biology, Loma Linda University School of Medicine, Loma Linda, CA 92350, USA.
authors: Richard B
authors: RB
authors: Thorpe
authors: Sara L
authors: SL
authors: Stockman
authors: James M
authors: JM
authors: Williams
authors: Thomas M
authors: TM
authors: Lincoln
authors: William J
authors: WJ
authors: Pearce
mesh_terms: D000375:Aging / Q000502:physiology; D000818:Animals; D015153:Blotting, Western; D002339:Carotid Arteries / Q000187:drug effects*; D002908:Chronic Disease; D006152:Cyclic GMP / Q000031:analogs & derivatives / Q000494:pharmacology; D017869:Cyclic GMP-Dependent Protein Kinases / Q000502:physiology*; D004305:Dose-Response Relationship, Drug; D023381:Endpoint Determination; D005260:Female; D005333:Fetus / Q000502:physiology; D000860:Hypoxia / Q000503:physiopathology*; D051036:Large-Conductance Calcium-Activated Potassium Channels / Q000502:physiology; D009131:Muscle, Smooth, Vascular / Q000187:drug effects*; D010766:Phosphorylation; D011247:Pregnancy; D044402:Receptor, Serotonin, 5-HT2A / Q000187:drug effects / Q000502:physiology; D012701:Serotonin / Q000494:pharmacology / Q000502:physiology*; D017366:Serotonin Receptor Agonists / Q000378:metabolism / Q000494:pharmacology; D012756:Sheep; D013873:Thionucleotides / Q000494:pharmacology
chemical_list: D051036:Large-Conductance Calcium-Activated Potassium Channels; D044402:Receptor, Serotonin, 5-HT2A; D017366:Serotonin Receptor Agonists; D013873:Thionucleotides; D012701:Serotonin; C055656:8-((4-chlorophenyl)thio)cyclic-3',5'-GMP; D017869:Cyclic GMP-Dependent Protein Kinases; D006152:Cyclic GMP
keywords: cGMP; chronic hypoxia; guanylate cyclase; iberiotoxin; postnatal maturation