Effects of salinity on intestinal bicarbonate secretion and compensatory regulation of acid-base balance in Opsanus beta
Effects of salinity on intestinal bicarbonate secretion and compensatory regulation of acid-base balance in Opsanus beta
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DOI：
10.1242/jeb.016832
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发表时间：
2008-07-15
影响因子：
2.8
通讯作者：
Grosell, Martin
中科院分区：
文献类型：
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作者：
Genz, Janet;Taylor, Josi R.;Grosell, Martin
海洋硬骨鱼的胞外液浓度低于它们所处的环境，导致持续的水分损失，这可以通过饮用来弥补，肠道中的水分吸收是由摄取盐分驱动的。氯离子的吸收部分通过顶端的氯离子/HCO3-交换，HCO3-由跨上皮运输和/或碳酸酐酶介导的内源性上皮二氧化碳水合作用提供。二氧化碳的水合作用也释放了H+，H+通过基底膜运输。在本研究中，海湾蟾鱼(Opsanus Beta)被驯化到9、35和50ppt。检查肠道HCO3的分泌、水和盐的吸收，以及随后对酸碱平衡的影响。直肠液排泄量随着盐度的增加而显著增加，从9ppt的0.17+/-0.05mlkg(-1)h(-1)增加到35ppt的0.70+/-0.19ml kg(-1)h(-1)和50ppt的1.46+/-0.22mlkg(-1)h(-1)。直肠液成分和排泄率可用于估计饮水率，当盐度从1.38+/-0.30增加到2.60+/-0.92和3.82+/-0.58ml kg(-1)h(-1)时，分别为9、35和50ppt。相比之下，吸水比例从9ppt的85.9+/-3.8%下降到35ppt的68.8+/-3.2%和50ppt的61.4+/-1.0%。尽管在9ppt、35ppt和50ppt时，直肠底部排泄量分别从9.3+/-2.7ppt和193.2+/-64.9mmolkg(-1)h(-1)分别降至68.2+/-20.4和193.2+/-64.9mmolkg(-1)h(-1)，但急性或长期暴露于改变的盐度仅与轻度酸碱平衡紊乱有关。肠道外，可能是鳃，净排出的酸随着盐度的增加而增加(9，35和50ppt分别为62.0+/-21.0,229.7+/-38.5和403.1+/-32.9mmolkg(-1)h(-1))，表明了对与渗透压调节需求相关的肠基分泌改变的代偿反应。
Marine teleosts have extracellular fluids less concentrated than their environment, resulting in continual water loss, which is compensated for by drinking, with intestinal water absorption driven by NaCl uptake. Absorption of Cl- occurs in part by apical Cl-/ HCO3- exchange, with HCO3- provided by transepithelial transport and/or by carbonic anhydrase-mediated hydration of endogenous epithelial CO2. Hydration of CO2 also liberates H+, which is transported across the basolateral membrane. In this study, gulf toadfish ( Opsanus beta) were acclimated to 9, 35 and 50 ppt. Intestinal HCO3- secretion, water and salt absorption, and the ensuing effects on acid-base balance were examined. Rectal fluid excretion greatly increased with increasing salinity from 0.17 +/- 0.05 mlkg(-1) h(-1) in 9 ppt to 0.70 +/- 0.19ml kg(-1)h(-1) in 35 ppt and 1.46 +/- 0.22ml kg(-1)h(-1) in 50 ppt. Rectal fluid composition and excretion rates allowed for estimation of drinking rates, which increased with salinity from 1.38 +/- 0.30 to 2.60 +/- 0.92 and 3.82 +/- 0.58ml kg(-1)h(-1) in 9, 35 and 50 ppt, respectively. By contrast, the fraction of imbibed water absorbed decreased from 85.9 +/- 3.8% in 9 ppt to 68.8 +/- 3.2% in 35 ppt and 61.4 +/- 1.0% in 50 ppt. Despite large changes in rectal base excretion from 9.3 +/- 2.7 to 68.2 +/- 20.4 and 193.2 +/- 64.9 mu mol kg(-1)h(-1) in 9, 35 and 50 ppt, respectively, acute or prolonged exposure to altered salinities was associated with only modest acid-base balance disturbances. Extra-intestinal, presumably branchial, net acid excretion increased with salinity ( 62.0 +/- 21.0, 229.7 +/- 38.5 and 403.1 +/- 32.9 mu mol kg(-1)h(-1) at 9, 35 and 50 ppt, respectively), demonstrating a compensatory response to altered intestinal base secretion associated with osmoregulatory demand.