在低 pH 值的软水条件下，随着 Al 浓度的升高，大型溞（Straus）的 Na 内流和外流的变化。

Changes in Na influx and outflux in Daphnia magna (Straus) as a function of elevated Al concentrations in soft water at low pH.

机构信息

Section of Ecology and Systematics, Cornell University, Ithaca, NY 14853.

出版信息

Proc Natl Acad Sci U S A. 1985 Nov;82(21):7345-9. doi: 10.1073/pnas.82.21.7345.

DOI:10.1073/pnas.82.21.7345

PMID:16593623

原文链接:https://pmc.ncbi.nlm.nih.gov/articles/PMC391341/

Abstract

The effects of aluminum (Al) on sodium (Na) regulation by the freshwater crustacean Daphnia magna were determined. (22)Na influx and outflux experiments were conducted in soft water adjusted to pH 4.5, 5.0, and 6.5 (reference pH) with either ambient (0.02 mg/liter) or high (1.02 mg/liter) concentrations of total Al. The results indicate that Al toxicity was pH dependent. Aluminum increased the rate of morbidity of D. magna at pH 6.5, had no additional effect to those of hydrogen ions (H(+)) at pH 5.0, and reduced the rate of morbidity at pH 4.5. Both H(+) and total Al concentrations interfered with Na regulation, although it was possible to distinguish between their respective effects by using (22)Na. At pH 6.5, Al decreased (22)Na influx (by 46%) and increased (22)Na outflux (by 25%), which led to a net loss of Na. At pH 5.0, Al reduced (22)Na influx (by 58%) but had no additional effect to that of H(+) on (22)Na outflux. At pH 4.5, (22)Na influx was significantly inhibited (by 73%) compared with the reference pH 6.5 treatment even in the absence of Al. Aluminum decreased (22)Na outflux (by 31%) at pH 4.5, which reduced the net loss of Na and temporarily prolonged survival of the daphnids. These results indicate that Al affects both (22)Na influx and outflux in D. magna. The lower rate of Na uptake may involve a denaturation of the enzyme responsible for the active uptake of Na. At pH 6.5, the increased outflux of (22)Na may be due to either increased membrane permeability or increased renal losses (or both). At pH 4.5, the reduced outflux of (22)Na resembles the amelioration that occurs in the presence of elevated Ca concentrations.

摘要

研究了淡水甲壳类动物大型溞（Daphnia magna）中铝（Al）对钠（Na）调节的影响。在 pH 值分别为 4.5、5.0 和 6.5（参考 pH 值）的软水中进行了 22Na 流入和流出实验，并用环境（0.02 毫克/升）或高（1.02 毫克/升）浓度的总 Al 进行了调节。结果表明，铝的毒性与 pH 值有关。铝在 pH 值为 6.5 时增加了大型溞的发病率，在 pH 值为 5.0 时对氢离子（H(+)）没有额外影响，而在 pH 值为 4.5 时降低了发病率。H(+) 和总 Al 浓度均干扰了 Na 调节，尽管可以通过使用 22Na 来区分它们各自的影响。在 pH 值为 6.5 时，Al 降低了 22Na 的流入（减少了 46%）并增加了 22Na 的流出（增加了 25%），导致 Na 的净损失。在 pH 值为 5.0 时，Al 降低了 22Na 的流入（减少了 58%），但对 H(+) 对 22Na 流出的影响没有额外作用。在 pH 值为 4.5 时，与参考 pH 值 6.5 处理相比，22Na 的流入明显受到抑制（减少了 73%），即使在没有 Al 的情况下也是如此。Al 降低了 22Na 的流出（减少了 31%）在 pH 值为 4.5 时，这减少了 Na 的净损失，并暂时延长了溞的存活时间。这些结果表明，Al 影响大型溞中 22Na 的流入和流出。Na 摄取率的降低可能涉及负责主动摄取 Na 的酶的变性。在 pH 值为 6.5 时，22Na 流出增加可能是由于膜通透性增加或肾损失增加（或两者兼有）。在 pH 值为 4.5 时，22Na 流出减少类似于在升高的 Ca 浓度存在下发生的改善。