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Campo DC | Valor | Idioma |
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dc.contributor.author | Wood, Chris M. | - |
dc.contributor.author | Kajimura, Makiko | - |
dc.contributor.author | Sloman, Katherine A. | - |
dc.contributor.author | Scott, Graham R. | - |
dc.contributor.author | Walsh, Patrick J. | - |
dc.contributor.author | Val, Vera Maria Fonseca Almeida e | - |
dc.contributor.author | Val, Adalberto Luis | - |
dc.date.accessioned | 2020-06-15T22:02:28Z | - |
dc.date.available | 2020-06-15T22:02:28Z | - |
dc.date.issued | 2007 | - |
dc.identifier.uri | https://repositorio.inpa.gov.br/handle/1/18664 | - |
dc.description.abstract | The Amazonian oscar is extremely resistant to hypoxia, and tolerance scales with size. Overall, ionoregulatory responses of small (∼15 g) and large oscars (∼200 g) to hypoxia were qualitatively similar, but the latter were more effective. Large oscars exhibited a rapid reduction in unidirectional Na+ uptake rate at the gills during acute hypoxia (PO2 ∼ 10 mmHg), which intensified with time (7 or 8 h); Na+ efflux rates were also reduced, so net balance was little affected. The inhibitions were virtually immediate (1st h) and preceded a later 60% reduction (at 3 h) in gill Na+-K+-ATPase activity, reflected in a 60% reduction in maximum Na+ uptake capacity without change in affinity (Km) for Na+. Upon acute restoration of normoxia, recovery of Na+ uptake was delayed for 1 h. These data suggest that dual mechanisms may be involved (e.g., immediate effects of O2 availability on transporters, channels, or permeability, slower effects of Na+-K +-ATPase regulation). Ammonia excretion appeared to be linked indirectly to Na+ uptake, exhibiting a Michaelis-Menten relationship with external [Na+], but the Km was less than for Na+ uptake. During hypoxia, ammonia excretion fell in a similar manner to Na + fluxes, with a delayed recovery upon normoxia restoration, but the relationship with [Na+] was blocked. Reductions in ammonia excretion were greater than in urea excretion. Plasma ammonia rose moderately over 3 h hypoxia, suggesting that inhibition of excretion was greater than inhibition of ammonia production. Overall, the oscar maintains excellent homeostasis of ionoregulation and N-balance during severe hypoxia. Copyright © 2007 the American Physiological Society. | en |
dc.language.iso | en | pt_BR |
dc.relation.ispartof | Volume 292, Número 5, Pags. R2048-R2058 | pt_BR |
dc.rights | Restrito | * |
dc.subject | Adenosine Triphosphatase (potassium Sodium) | en |
dc.subject | Ammonia Formation | en |
dc.subject | Anaerobic Capacity | en |
dc.subject | Atomic Absorption Spectrometry | en |
dc.subject | Disease Severity | en |
dc.subject | Enzyme Activity | en |
dc.subject | Hypoxia | en |
dc.subject | Michaelis Menten Kinetics | en |
dc.subject | Nitrogen Balance | en |
dc.subject | Nitrogen Metabolism | en |
dc.subject | Nitrogen Urine Level | en |
dc.subject | Nonhuman | en |
dc.subject | Priority Journal | en |
dc.subject | Sodium Transport | en |
dc.subject | Teleost | en |
dc.subject | Ammonia | en |
dc.subject | Animal | en |
dc.subject | Body Size | en |
dc.subject | Cichlids | en |
dc.subject | Environment | en |
dc.subject | Hydrogen-ion Concentration | en |
dc.subject | Oxygen | en |
dc.subject | Sodium | en |
dc.subject | Urea | en |
dc.subject | Water | en |
dc.subject | Water-electrolyte Balance | en |
dc.title | Rapid regulation of Na+ fluxes and ammonia excretion in response to acute environmental hypoxia in the Amazonian oscar, Astronotus ocellatus | en |
dc.type | Artigo | pt_BR |
dc.identifier.doi | 10.1152/ajpregu.00640.2006 | - |
dc.publisher.journal | American Journal of Physiology-regulatory Integrative and Comparative Physiology | pt_BR |
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