草食性硬骨鱼肠道中Na⁺和Cl⁻转运的平行反向转运机制。

Parallel antiport mechanisms for Na+ and Cl- transport in herbivorous teleost intestine.

作者信息

Howard J N, Ahearn G A

机构信息

Department of Zoology, University of Hawaii at Manoa, Honolulu 96822.

出版信息

J Exp Biol. 1988 Mar;135:65-76. doi: 10.1242/jeb.135.1.65.

DOI:10.1242/jeb.135.1.65

PMID:3373145

Abstract

Transport mechanisms for NaCl in intestinal brush border membrane vesicles (BBMV) of herbivorous, seawater-adapted tilapia, Oreochromis mossambicus, were investigated with a rapid filtration technique using 22Na+ and 36Cl- as tracers. Evidence to support the existence of cotransport mechanisms (Na+/Cl- or Na+/K+/2Cl-) in tilapia intestinal BBMV was not found. An inwardly directed Cl- gradient or KCl gradient did not stimulate the uptake of Na+ into tilapia intestinal BBMV. Furthermore, the uptake of Na+ under these conditions was not significantly affected by furosemide. Evidence was found to indicate the existence of Na+/H+ and Cl-/HCO3- antiport mechanisms for NaCl transport in tilapia intestinal BBMV. An outwardly directed proton gradient (pH 6.0 in, pH 7.5 out) stimulated the uptake of Na+ above that of the control (pH 7.5 in, pH 7.5 out). Exogenous amiloride (1 mmol l-1) significantly reduced Na+ uptake in the presence of an outwardly directed proton gradient. Apparent influxes of 1 mmol l-1 Na+ were (nmol mg protein -1 15 s-1 +/- 1 S.E.): control, 1.46 +/- 0.09; pH gradient, 3.36 +/- 0.14; pH gradient plus amiloride, 1.55 +/- 0.05. The uptake of Cl- was stimulated by outwardly directed HCO3- and Cl- gradients in comparison with an outwardly directed gluconate gradient. Apparent influxes of 10 mmol l-1 Cl- were (nmol mg protein-1 15 s-1 +/- 1 S.E.): gluconate, 12.90 +/- 0.19; HCO3-, 15.83 +/- 0.34; Cl-, 14.62 +/- 0.42. These results suggest that, in contrast to the cotransport mechanisms for NaCl that have been reported for other fish intestine, the herbivorous marine teleost, Oreochromis mossambicus, possesses dual antiport mechanisms for the transport of NaCl across its intestinal brush border membrane.

摘要

利用快速过滤技术，以²²Na⁺和³⁶Cl⁻作为示踪剂，研究了适应海水的草食性罗非鱼（莫桑比克罗非鱼）肠道刷状缘膜囊泡（BBMV）中NaCl的转运机制。未发现支持罗非鱼肠道BBMV中存在共转运机制（Na⁺/Cl⁻或Na⁺/K⁺/2Cl⁻）的证据。内向的Cl⁻梯度或KCl梯度并未刺激Na⁺进入罗非鱼肠道BBMV。此外，在这些条件下，呋塞米对Na⁺的摄取没有显著影响。有证据表明罗非鱼肠道BBMV中存在用于NaCl转运的Na⁺/H⁺和Cl⁻/HCO₃⁻反向转运机制。外向的质子梯度（内部pH 6.0，外部pH 7.5）刺激的Na⁺摄取高于对照组（内部pH 7.5，外部pH 7.5）。在存在外向质子梯度的情况下，外源性氨氯吡咪（1 mmol·l⁻¹）显著降低了Na⁺摄取。1 mmol·l⁻¹ Na⁺的表观流入量为（nmol·mg蛋白质⁻¹·15 s⁻¹±1标准误）：对照组，1.46±0.09；pH梯度组，3.36±0.14；pH梯度加氨氯吡咪组，1.55±0.05。与外向的葡萄糖酸盐梯度相比，外向的HCO₃⁻和Cl⁻梯度刺激了Cl⁻的摄取。10 mmol·l⁻¹ Cl⁻的表观流入量为（nmol·mg蛋白质⁻¹·15 s⁻¹±1标准误）：葡萄糖酸盐组，12.90±0.19；HCO₃⁻组，15.83±0.34；Cl⁻组，14.62±0.42。这些结果表明，与已报道的其他鱼类肠道中NaCl的共转运机制不同，草食性海洋硬骨鱼莫桑比克罗非鱼在其肠道刷状缘膜上具有用于NaCl转运的双重反向转运机制。