Bieczynski Flavia, Painefilú Julio C, Venturino Andrés, Luquet Carlos M
Centro de Investigaciones en Toxicología Ambiental y Agrobiotecnología del Comahue - Consejo Nacional de Investigaciones Científicas y Técnicas, Universidad Nacional del Comahue, Neuquén, Argentina.
Instituto Patagónico de Tecnologías Biológicas y Geoambientales, Consejo Nacional de Investigaciones Científicas y Técnicas - Universidad Nacional del Comahue, Bariloche, Argentina.
Front Physiol. 2021 Dec 9;12:791834. doi: 10.3389/fphys.2021.791834. eCollection 2021.
In fish, the intestine is fundamental for digestion, nutrient absorption, and other functions like osmoregulation, acid-base balance, and excretion of some metabolic products. These functions require a large exchange surface area, which, in turn, favors the absorption of natural and anthropogenic foreign substances (xenobiotics) either dissolved in water or contained in the food. According to their chemical nature, nutrients, ions, and water may cross the intestine epithelium cells' apical and basolateral membranes by passive diffusion or through a wide array of transport proteins and also through endocytosis and exocytosis. In the same way, xenobiotics can cross this barrier by passive diffusion or taking advantage of proteins that transport physiological substrates. The entry of toxic substances is counterbalanced by an active efflux transport mediated by diverse membrane proteins, including the ATP binding cassette (ABC) proteins. Recent advances in structure, molecular properties, and functional studies have shed light on the importance of these proteins in cellular and organismal homeostasis. There is abundant literature on mammalian ABC proteins, while the studies on ABC functions in fish have mainly focused on the liver and, to a minor degree, on the kidney and other organs. Despite their critical importance in normal physiology and as a barrier to prevent xenobiotics incorporation, fish intestine's ABC transporters have received much less attention. All the ABC subfamilies are present in the fish intestine, although their functionality is still scarcely studied. For example, there are few studies of ABC-mediated transport made with polarized intestinal preparations. Thus, only a few works discriminate apical from basolateral transport activity. We briefly describe the main functions of each ABC subfamily reported for mammals and other fish organs to help understand their roles in the fish intestine. Our study considers immunohistochemical, histological, biochemical, molecular, physiological, and toxicological aspects of fish intestinal ABC proteins. We focus on the most extensively studied fish ABC proteins (subfamilies ABCB, ABCC, and ABCG), considering their apical or basolateral location and distribution along the intestine. We also discuss the implication of fish intestinal ABC proteins in the transport of physiological substrates and aquatic pollutants, such as pesticides, cyanotoxins, metals, hydrocarbons, and pharmaceutical products.
在鱼类中，肠道对于消化、营养物质吸收以及其他功能（如渗透调节、酸碱平衡和某些代谢产物的排泄）至关重要。这些功能需要较大的交换表面积，这反过来又有利于吸收溶解在水中或食物中的天然和人为外来物质（异生素）。根据其化学性质，营养物质、离子和水可以通过被动扩散或通过多种转运蛋白，以及通过内吞作用和外排作用穿过肠上皮细胞的顶端和基底外侧膜。同样，异生素可以通过被动扩散或利用转运生理底物的蛋白质穿过这道屏障。有毒物质的进入通过由多种膜蛋白介导的主动外排转运来平衡，包括ATP结合盒（ABC）蛋白。结构、分子特性和功能研究的最新进展揭示了这些蛋白在细胞和机体稳态中的重要性。关于哺乳动物ABC蛋白有大量文献，而关于鱼类中ABC功能的研究主要集中在肝脏，在较小程度上集中在肾脏和其他器官。尽管鱼类肠道的ABC转运蛋白在正常生理功能以及作为防止异生素摄入的屏障方面至关重要，但受到的关注却少得多。所有ABC亚家族都存在于鱼类肠道中，尽管它们的功能仍很少被研究。例如，用极化肠道制剂进行的ABC介导转运的研究很少。因此，只有少数研究区分了顶端和基底外侧的转运活性。我们简要描述了报道的哺乳动物和其他鱼类器官中每个ABC亚家族的主要功能，以帮助理解它们在鱼类肠道中的作用。我们的研究考虑了鱼类肠道ABC蛋白的免疫组织化学、组织学、生物化学、分子、生理和毒理学方面。我们关注研究最广泛的鱼类ABC蛋白（ABCB、ABCC和ABCG亚家族），考虑它们在肠道中的顶端或基底外侧位置和分布。我们还讨论了鱼类肠道ABC蛋白在生理底物和水生污染物（如农药、蓝藻毒素、金属、碳氢化合物和药品）转运中的作用。
