Your browser doesn't support javascript.
loading
Mostrar: 20 | 50 | 100
Resultados 1 - 2 de 2
Filtrar
Mais filtros

Base de dados
Ano de publicação
Tipo de documento
Intervalo de ano de publicação
1.
Am J Physiol Regul Integr Comp Physiol ; 314(6): R870-R882, 2018 06 01.
Artigo em Inglês | MEDLINE | ID: mdl-29513562

RESUMO

Bradykinin-induced activation of the pulmonary endothelium triggers a rise in intracellular Ca2+ that activates nitric oxide (NO)-dependent vasorelaxation. Chronic hypoxia is commonly associated with increased pulmonary vascular tone, which can cause pulmonary hypertension in responsive individuals. In the present study, we tested the hypothesis that long-term high-altitude hypoxia (LTH) diminishes bradykinin-induced Ca2+ signals and inhibits endothelial nitric oxide synthase (eNOS), prostacyclin (PGI2), and large-conductance K+ (BKCa) channels in sheep, which are moderately responsive to LTH, resulting in decreased pulmonary arterial vasorelaxation. Pulmonary arteries were isolated from ewes kept near sea level (720 m) or at high altitude (3,801 m) for >100 days. Vessel force was measured with wire myography and endothelial intracellular Ca2+ with confocal microscopy. eNOS was inhibited with 100 µM NG-nitro-l-arginine methyl ester (l-NAME), PGI2 production was inhibited with 10 µM indomethacin that inhibits cyclooxygenase, and BKCa channels were blocked with 1 mM tetraethylammonium. Bradykinin-induced endothelial Ca2+ signals increased following LTH, but bradykinin relaxation decreased. Furthermore, some vessels contracted in response to bradykinin after LTH. l-NAME sensitivity decreased, suggesting that eNOS dysfunction played a role in uncoupling Ca2+ signals and bradykinin relaxation. The Ca2+ ionophore A-23187 (10 µM) elicited an enhanced Ca2+ response following LTH while relaxation was unchanged although l-NAME sensitivity increased. Additionally, BKCa function decreased during bradykinin relaxation following LTH. Western analysis showed that BKCa α-subunit expression was increased by LTH while that for the ß1 subunit was unchanged. Overall, these results suggest that those even moderately responsive to LTH can have impaired endothelial function.


Assuntos
Altitude , Sinalização do Cálcio/efeitos dos fármacos , Hipóxia/metabolismo , Óxido Nítrico Sintase Tipo III/metabolismo , Artéria Pulmonar/efeitos dos fármacos , Animais , Bradicinina/farmacologia , Inibidores Enzimáticos/farmacologia , Epoprostenol/metabolismo , Canais de Potássio Ativados por Cálcio de Condutância Alta/metabolismo , Contração Muscular/efeitos dos fármacos , Relaxamento Muscular/efeitos dos fármacos , NG-Nitroarginina Metil Éster/farmacologia , Óxido Nítrico Sintase Tipo III/antagonistas & inibidores , Ovinos
2.
Am J Physiol Lung Cell Mol Physiol ; 310(3): L271-86, 2016 Feb 01.
Artigo em Inglês | MEDLINE | ID: mdl-26637638

RESUMO

Bradykinin-induced activation of the pulmonary endothelium triggers nitric oxide production and other signals that cause vasorelaxation, including stimulation of large-conductance Ca(2+)-activated K(+) (BKCa) channels in myocytes that hyperpolarize the plasma membrane and decrease intracellular Ca(2+). Intrauterine chronic hypoxia (CH) may reduce vasorelaxation in the fetal-to-newborn transition and contribute to pulmonary hypertension of the newborn. Thus we examined the effects of maturation and CH on the role of BKCa channels during bradykinin-induced vasorelaxation by examining endothelial Ca(2+) signals, wire myography, and Western immunoblots on pulmonary arteries isolated from near-term fetal (∼ 140 days gestation) and newborn, 10- to 20-day-old, sheep that lived in normoxia at 700 m or in CH at high altitude (3,801 m) for >100 days. CH enhanced bradykinin-induced relaxation of fetal vessels but decreased relaxation in newborns. Endothelial Ca(2+) responses decreased with maturation but increased with CH. Bradykinin-dependent relaxation was sensitive to 100 µM nitro-L-arginine methyl ester or 10 µM 1H-[1,2,4]oxadiazolo[4,3-a]quinoxalin-1-one, supporting roles for endothelial nitric oxide synthase and soluble guanylate cyclase activation. Indomethacin blocked relaxation in CH vessels, suggesting upregulation of PLA2 pathways. BKCa channel inhibition with 1 mM tetraethylammonium reduced bradykinin-induced vasorelaxation in the normoxic newborn and fetal CH vessels. Maturation reduced whole cell BKCa channel α1-subunit expression but increased ß1-subunit expression. These results suggest that CH amplifies the contribution of BKCa channels to bradykinin-induced vasorelaxation in fetal sheep but stunts further development of this vasodilatory pathway in newborns. This involves complex changes in multiple components of the bradykinin-signaling axes.


Assuntos
Bradicinina/metabolismo , Hipóxia/metabolismo , Vasodilatação/fisiologia , Animais , Arginina/análogos & derivados , Arginina/metabolismo , Endotélio Vascular/crescimento & desenvolvimento , Endotélio Vascular/metabolismo , Óxido Nítrico/metabolismo , Óxido Nítrico Sintase Tipo III/metabolismo , Artéria Pulmonar/crescimento & desenvolvimento , Artéria Pulmonar/metabolismo , Ovinos
SELEÇÃO DE REFERÊNCIAS
Detalhe da pesquisa