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首页> 外文期刊>American Journal of Physiology >Rapid regulation of Na+ fluxes and ammonia excretion in response to acute environmental hypoxia in the Amazonian oscar, Astronotus ocellatus.
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Rapid regulation of Na+ fluxes and ammonia excretion in response to acute environmental hypoxia in the Amazonian oscar, Astronotus ocellatus.

机译：快速反应调节Na +通量和氨气排泄，以响应亚马逊奥斯卡天星小球藻的急性环境低氧。

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摘要

The Amazonian oscar is extremely resistant to hypoxia, and tolerance scales with size. Overall, ionoregulatory responses of small ( approximately 15 g) and large oscars ( approximately 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 (Po(2) approximately 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 O(2) 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.
机译：亚马孙州的奥斯卡对缺氧具有极强的抵抗力，耐受力随大小而变。总体而言，小（约15 g）和大奥斯卡（约200 g）对缺氧的离子调节反应在质量上相似，但后者更为有效。大型奥斯卡在急性缺氧（Po（2）约10 mmHg）期间，ill表现出单向Na（+）吸收速率的快速降低，随着时间的增加（7或8 h）; Na（+）外排率也降低了，因此净平衡几乎没有受到影响。抑制作用几乎是即时的（第1小时），随后g（Na +）-K（+）-ATPase活性降低了60％（3小时），这反映出最大Na（+）吸收能力降低了60％对Na（+）的亲和力（Km）不变。急性恢复正常血症后，Na（+）吸收的恢复延迟了1小时。这些数据表明可能涉及双重机制（例如，O（2）可用性对转运蛋白，通道或通透性的直接影响，Na（+）-K（+）-ATPase调控的较慢影响）。氨的排泄似乎与Na（+）的吸收间接相关，表现出与外部[Na（+）]的Michaelis-Menten关系，但Km小于Na（+）的吸收。在缺氧期间，氨的排泄量以与Na（+）通量相似的方式下降，恢复了正常氧恢复后的延迟，但与[Na（+）]的关系被阻止。氨的排泄减少量大于尿素的排泄量。缺氧3小时后，血浆氨适度上升，表明对排泄的抑制作用大于对氨产生的抑制作用。总体而言，在严重缺氧期间，奥斯卡保持了离子调节和N平衡的极佳稳态。

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