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Ausencia de unión cooperativa hemoglobina-oxígeno en el Sphenodon, una reliquia reptiliana del Triásico
Nature
|December 1, 1983
Resumen
La curva de disociación hemoglobina-oxígeno en Sphenodon punctatus es singularmente hiperbólica, no sigmoidal. Este hallazgo desafía el modelo aceptado para el transporte eficiente de oxígeno en vertebrados terrestres.
Área de la Ciencia:
- Fisiología comparativa de la fisiología.
- Los sistemas respiratorios de los vertebrados tienen
- La bioquímica del transporte de oxígeno.
Sus antecedentes:
- La curva de disociación sigmoidal hemoglobina-oxígeno (ODC) y el efecto Bohr se consideran esenciales para el transporte eficiente de oxígeno en los vertebrados terrestres.
- Estas características facilitan grandes cambios de volumen de oxígeno con pequeñas variaciones de presión parcial de oxígeno (PO2) y se observan en reptiles, aves y mamíferos.
- Esto incluye especies adaptadas a entornos extremos como el buceo, la excavación y las grandes alturas.
Objetivo del estudio:
- Para investigar las propiedades de transporte de oxígeno de la sangre de Sphenodon punctatus, la única especie sobreviviente del antiguo orden Rhynchocephalia.
- Para determinar si Sphenodon exhibe el típico sigmoidal ODC y el efecto de Bohr visto en otros vertebrados terrestres.
- Comprender las implicaciones de las características respiratorias únicas de Sphenodon en el contexto de su historia evolutiva y nicho ecológico.
Principales métodos:
- Análisis de las características de unión de oxígeno en sangre en Sphenodon.
- Determinación de la forma de la curva de disociación hemoglobina-oxígeno (ODC).
- Cuantificación de la magnitud del efecto Bohr.
Principales resultados:
- Sphenodon punctatus exhibe un ODC hiperbólico, que se desvía de la forma sigmoidal generalmente aceptada en los vertebrados terrestres.
- La sangre muestra una alta afinidad por el oxígeno.
- Se observó un efecto de Bohr muy pequeño, lo que indica una sensibilidad limitada a los cambios en la acidez sanguínea (relacionada con los niveles de CO2).
Conclusiones:
- El ODC hiperbólico y el mínimo efecto de Bohr en Sphenodon son únicos entre los vertebrados terrestres.
- Estas características sugieren una baja demanda de oxígeno y una capacidad limitada para la actividad aeróbica en Sphenodon.
- Este perfil fisiológico único proporciona información sobre las diversas estrategias evolutivas para el transporte de oxígeno en los vertebrados.
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