PDF(Pubmed)
Abstract：
Aquatic animals residing in saline habitats either allow extracellular sodium concentration to conform to environmental values or regulate sodium to lower levels. The latter strategy requires an energy-driven process to move sodium against a large concentration gradient to eliminate excess sodium that diffuses into the animal. Previous studies of invertebrate and vertebrate species indicate a sodium pump, Na+/K+ ATPase, powers sodium secretion. We provide the first functional evidence of a saline-water animal, Aedes taeniorhynchus mosquito larva, utilizing a proton pump to power this process. Vacuolar-type H+ ATPase (VHA) protein is highly expressed on the apical membrane of the posterior rectal cells, and in situ sodium flux across this epithelium increases significantly in larvae held in higher salinity and is sensitive to Bafilomycin A1, an inhibitor of VHA. We also report the first evidence of splice variants of the sodium/proton exchanger, NHE3, with both high and low molecular weight variants highly expressed on the apical membrane of the posterior rectal cells. Evidence of NHE3 function was indicated with in situ sodium transport significantly inhibited by a NHE3 antagonist, S3226. We propose that the outward proton pumping by VHA establishes a favourable electromotive gradient to drive sodium secretion via NHE3 thus producing a hyperosmotic, sodium-rich urine. This H+- driven Na+ secretion process is the primary mechanism of ion regulation in salt-tolerant culicine mosquito species and was first investigated over 80 years ago.
摘要：
居住在盐水栖息地的水生动物要么允许细胞外钠浓度符合环境值，要么将钠调节到较低水平。后一种策略需要能量驱动的过程来使钠相对于大的浓度梯度移动，以消除扩散到动物体内的过量钠。以前对无脊椎动物和脊椎动物物种的研究表明，钠泵，Na+/K+ATP酶,促进钠分泌。我们提供了盐水动物的第一个功能证据，伊蚊蚊幼虫，利用质子泵为这个过程提供动力。空泡型H+ATPase(VHA)蛋白在直肠后细胞顶膜高表达,在盐度较高的幼虫中，穿过该上皮的原位钠通量显着增加，并且对VHA的抑制剂巴弗洛霉素A1敏感。我们还报道了钠/质子交换体剪接变体的第一个证据，NHE3，高分子量和低分子量变体在直肠后细胞的顶膜上高度表达。NHE3功能的证据表明，NHE3拮抗剂显著抑制了原位钠转运，S3226.我们建议VHA的向外质子泵浦建立了有利的电动势梯度，以通过NHE3驱动钠分泌，从而产生高渗，富含钠的尿液.这种H驱动的Na分泌过程是耐盐孔雀石蚊子物种中离子调节的主要机制，并且在80多年前首次进行了研究。
