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银大麻哈鱼(Oncorhynchus kisutch)经口暴露后软骨藻酸的摄取、组织分布及排泄

Uptake, tissue distribution and excretion of domoic acid after oral exposure in coho salmon (Oncorhynchus kisutch).

作者信息

Lefebvre Kathi A, Noren Dawn P, Schultz Irvin R, Bogard Sara M, Wilson Jacquelyn, Eberhart Bich-Thuy L

机构信息

NOAA Fisheries, Northwest Fisheries Science Center, Environmental Conservation Division, Marine Biotoxins Program, 2725 Montlake Blvd. East, Seattle, WA 98112, USA.

出版信息

Aquat Toxicol. 2007 Mar 10;81(3):266-74. doi: 10.1016/j.aquatox.2006.12.009. Epub 2007 Jan 3.

Abstract

Domoic acid (DA) is a potent neurotoxin naturally produced by some pennate diatom species of the genus Pseudo-nitzschia. It is well known that during harmful algal blooms fish can accumulate DA in the gastrointestinal (GI) tract and act as vectors of the toxin to higher trophic level piscivores, often with severe neurotoxic consequences to the predators. Although neurotoxicity and mass mortality have been observed in vertebrates (i.e. marine mammals and sea birds) feeding on contaminated fish, to date there has been no evidence of neurobehavioral toxicity in the fish vectors themselves. It has been hypothesized that fish may not absorb DA from the digestive tract, thus making them insensitive to dietary consumption of DA. To test this hypothesis, we performed oral gavage exposures followed by a time series of tissue dissections to characterize uptake, depuration, and tissue distribution of DA in fish. Intracoelomic (IC) injection exposures (which bypass the GI tract) were also performed to determine if coho neurons are neurologically susceptible to DA. Excitotoxic symptoms were observed in fish via IC injection at similar toxin levels that have been reported to induce excitotoxic symptoms in intraperitoneal (IP) exposures with mammalian models such as mice, suggesting that fish neurons have a similar sensitivity to DA as other vertebrates. Surprisingly, after oral gavage with ecologically relevant doses of DA, the toxin was detected in plasma collected from the dorsal aorta via a permanent intraarterial catheter within 15 min, yet excitotoxic symptoms were not observed. Additionally, DA was detected in liver, heart, spleen, kidney, muscle, brain and bile. These data indicate that although DA is absorbed from the gut, fish do not exhibit neuroexcitatory effects at maximum ecologically relevant oral doses of DA. Tissue distribution and DA uptake and depuration patterns suggest that a majority of the absorbed toxin is excreted via the kidneys and bile, thereby preventing toxic levels of DA from reaching sensitive nervous tissue. Additionally, greater than 20% of total IC administered DA doses were sequestered in bile within 1h of injection in five symptomatic fish, providing evidence for biliary sequestration of the toxin from blood. Here, we comprehensively describe the uptake, depuration, and tissue distribution patterns of DA and propose that renal and biliary processes may serve as primary routes of toxin clearance in fish.

摘要

软骨藻酸(DA)是一种由伪菱形藻属的一些羽纹硅藻自然产生的强效神经毒素。众所周知,在有害藻华期间,鱼类会在胃肠道(GI)中积累DA,并作为毒素载体将其传递给营养级更高的食鱼动物,这通常会给捕食者带来严重的神经毒性后果。尽管在以受污染鱼类为食的脊椎动物(即海洋哺乳动物和海鸟)中观察到了神经毒性和大量死亡,但迄今为止,尚未有证据表明鱼类载体本身存在神经行为毒性。据推测,鱼类可能不会从消化道吸收DA,因此对通过饮食摄入的DA不敏感。为了验证这一假设,我们进行了口服灌胃暴露,随后进行了一系列组织解剖,以表征DA在鱼类中的摄取、净化和组织分布情况。还进行了体腔(IC)注射暴露(绕过胃肠道),以确定银大麻哈鱼神经元对DA是否具有神经易感性。在与哺乳动物模型(如小鼠)腹腔内(IP)暴露中诱导兴奋毒性症状的类似毒素水平下,通过IC注射在鱼类中观察到了兴奋毒性症状,这表明鱼类神经元对DA的敏感性与其他脊椎动物相似。令人惊讶的是,在用生态相关剂量的DA进行口服灌胃后,在15分钟内通过永久性动脉内导管从背主动脉采集的血浆中检测到了该毒素,但未观察到兴奋毒性症状。此外,在肝脏、心脏、脾脏、肾脏、肌肉、大脑和胆汁中也检测到了DA。这些数据表明,尽管DA是从肠道吸收的,但在最大生态相关口服剂量的DA下,鱼类并未表现出神经兴奋作用。组织分布以及DA的摄取和净化模式表明,大部分吸收的毒素通过肾脏和胆汁排出,从而防止DA的毒性水平到达敏感的神经组织。此外,在五条出现症状的鱼类中,超过20%的IC注射总剂量的DA在注射后1小时内被隔离在胆汁中,这为毒素从血液中被胆汁隔离提供了证据。在这里,我们全面描述了DA的摄取、净化和组织分布模式,并提出肾脏和胆汁过程可能是鱼类毒素清除的主要途径。

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