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The fetal llama versus the fetal sheep: different strategies to withstand hypoxia.
Llanos, Aníbal J; Riquelme, Raquel A; Sanhueza, Emilia M; Hanson, Mark A; Blanco, Carlos E; Parer, Julian T; Herrera, Emilio A; Pulgar, Victor M; Reyes, Roberto V; Cabello, Gertrudis; Giussani, Dino A.
Afiliação
  • Llanos AJ; Laboratorio de Fisiología y Fisiopatología del Desarrollo, Programa de Fisiopatología, Instituto de Ciencias Biomédicas, Facultad de Medicina, Universidad de Chile, Santiago, Chile. allanos@machi.med.uchile.cl
High Alt Med Biol ; 4(2): 193-202, 2003.
Article em En | MEDLINE | ID: mdl-12855051
The pregnant llama (Lama glama) has walked for millions of years through the thin oxygen trail of the Andean altiplano. We hypothesize that a pool of genes has been selected in the llama that express efficient mechanisms to withstand this low-oxygen milieu. The llama fetus responds to acute hypoxia with an intense peripheral vasoconstriction that is not affected by bilateral section of the carotid sinus nerves. Moreover, the increase in fetal plasma concentrations of vasoconstrictor hormones, such as catecholamines, neuropeptide Y, and vasopressin, is much greater in the llama than in the sheep fetus. Furthermore, treatment of fetal llamas with an alpha-adrenergic antagonist abolished the peripheral vasoconstriction and resulted in fetal cardiovascular collapse and death during acute hypoxia, suggesting an indispensable upregulation of alpha-adrenergic mechanisms in this high altitude species. Local endothelial factors such as nitric oxide (NO) also play a key role in the regulation of fetal adrenal blood flow and in the adrenal secretion of catecholamines and cortisol. Interestingly, in contrast to the human or sheep fetus, the llama fetus showed a small increase in brain blood flow during acute hypoxia, with no increase in oxygen extraction across the brain, and thereby a decrease in brain oxygen consumption. These results suggest that the llama fetus responds to acute hypoxia with hypometabolism. How this reduction in metabolism is produced and how the cells are preserved during this condition remain to be elucidated.
Assuntos
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Coleções: 01-internacional Base de dados: MEDLINE Assunto principal: Camelídeos Americanos / Ovinos / Adaptação Fisiológica / Hipóxia Limite: Animals / Female / Humans / Pregnancy Idioma: En Revista: High Alt Med Biol Assunto da revista: BIOLOGIA / MEDICINA Ano de publicação: 2003 Tipo de documento: Article País de afiliação: Chile País de publicação: Estados Unidos
Buscar no Google
Coleções: 01-internacional Base de dados: MEDLINE Assunto principal: Camelídeos Americanos / Ovinos / Adaptação Fisiológica / Hipóxia Limite: Animals / Female / Humans / Pregnancy Idioma: En Revista: High Alt Med Biol Assunto da revista: BIOLOGIA / MEDICINA Ano de publicação: 2003 Tipo de documento: Article País de afiliação: Chile País de publicação: Estados Unidos