Brijs Jeroen, Hennig Grant W, Gräns Albin, Dekens Esmée, Axelsson Michael, Olsson Catharina
Department of Biological and Environmental Sciences, University of Gothenburg, SE-405 30 Gothenburg, Sweden
Department of Pharmacology, University of Vermont, College of Medicine, Burlington, VT 05405, USA.
J Exp Biol. 2017 Jul 1;220(Pt 13):2397-2408. doi: 10.1242/jeb.156000. Epub 2017 Apr 21.
Upon exposure to seawater, euryhaline teleosts need to imbibe and desalinate seawater to allow for intestinal ion and water absorption, as this is essential for maintaining osmotic homeostasis. Despite the potential benefits of increased mixing and transport of imbibed water for increasing the efficiency of absorptive processes, the effect of water salinity on intestinal motility in teleosts remains unexplored. By qualitatively and quantitatively describing intestinal motility of euryhaline rainbow trout (), this study demonstrates that, in freshwater, the most common motility pattern consisted of clusters of rhythmic, posteriorly propagating contractions that lasted ∼1-2 min followed by a period of quiescence lasting ∼4-5 min. This pattern closely resembles mammalian migrating motor complexes (MMCs). Following a transition to seawater, imbibed seawater resulted in a significant distension of the intestine and the frequency of MMCs increased twofold to threefold with a concomitant reduction in the periods of quiescence. The increased frequency of MMCs was also accompanied by ripple-type contractions occurring every 12-60 s. These findings demonstrate that intestinal contractile activity of euryhaline teleosts is dramatically increased upon exposure to seawater, which is likely part of the overall response for maintaining osmotic homeostasis as increased drinking and mechanical perturbation of fluids is necessary to optimise intestinal ion and water absorption. Finally, the temporal response of intestinal motility in rainbow trout transitioning from freshwater to seawater coincides with previously documented physiological modifications associated with osmoregulation and may provide further insight into the underlying reasons shaping the migration patterns of salmonids.
广盐性硬骨鱼在接触海水时，需要摄取并淡化海水，以便进行肠道离子和水分吸收，因为这对于维持渗透平衡至关重要。尽管摄取的水增加混合和运输可能有利于提高吸收过程的效率，但水盐度对硬骨鱼肠道蠕动的影响仍未得到探索。通过定性和定量描述广盐性虹鳟鱼（）的肠道蠕动，本研究表明，在淡水中，最常见的蠕动模式是由有节奏的、向后传播的收缩簇组成，持续约1-2分钟，随后是约4-5分钟的静止期。这种模式与哺乳动物的移行性运动复合波（MMC）非常相似。过渡到海水后，摄取的海水导致肠道明显扩张，MMC的频率增加了两倍到三倍，同时静止期缩短。MMC频率的增加还伴随着每12-60秒出现一次的涟漪式收缩。这些发现表明，广盐性硬骨鱼在接触海水后肠道收缩活动显著增加，这可能是维持渗透平衡的整体反应的一部分，因为增加饮水和对液体的机械扰动对于优化肠道离子和水分吸收是必要的。最后，虹鳟鱼从淡水过渡到海水时肠道蠕动的时间反应与先前记录的与渗透压调节相关的生理变化一致，可能会进一步深入了解塑造鲑科鱼类洄游模式的潜在原因。
