Catches Justin S, Burns Julie M, Edwards Susan L, Claiborne James B
Department of Biology, Georgia Southern University, Statesboro, 30460, USA.
J Exp Biol. 2006 Sep;209(Pt 17):3440-7. doi: 10.1242/jeb.02384.
Long-term pH compensation in a marine teleost requires the transepithelial excretion of H(+) across the gill epithelium. H(+) efflux in the longhorn sculpin (Myoxocephalus octodecemspinosus) is dependent on external sodium ion concentration and is inhibited by known inhibitors of Na(+)/H(+) exchangers. Our model for proton transport suggests acid-excreting cells in the gill with an apical Na(+)/H(+) antiporter and basolateral Na(+)/K(+)-ATPase. This model is similar to mammalian kidney and elasmobranch gill epithelium in which a basolateral electrogenic-vacuolar proton pump (V-H(+)-ATPase) localizes to base-excreting cells. The objective of this study was to detect the presence and location of membrane transporters in marine fish gills using immunohistochemical staining. Our data indicate the presence of an apical and subapical Na(+)/H(+)-exchanger 2 (NHE2) in the sculpin gill. NHE2 is present in large, ovoid chloride cells and often colocalizes in the same cells as Na(+)/K(+)-ATPase. We also detected V-H(+)-ATPase immunoreactivity, predominantly in cells at the base of the lamellae, with staining patterns indicative of a basolateral location. The 85 kDa protein detected on immunoblots with anti-NHE2 antibodies was found in both control and acid-infused animals and did not change following a large acute acidosis over 8 h.
海洋硬骨鱼的长期pH值补偿需要通过鳃上皮进行跨上皮H⁺排泄。长角杜父鱼（Myoxocephalus octodecemspinosus）中的H⁺外流依赖于外部钠离子浓度，并受到已知的Na⁺/H⁺交换体抑制剂的抑制。我们的质子运输模型表明，鳃中的排酸细胞具有顶端Na⁺/H⁺反向转运体和基底外侧Na⁺/K⁺-ATP酶。该模型类似于哺乳动物肾脏和板鳃类鳃上皮，其中基底外侧的电生性液泡质子泵（V-H⁺-ATP酶）定位于排碱细胞。本研究的目的是使用免疫组织化学染色检测海洋鱼类鳃中膜转运体的存在和位置。我们的数据表明，杜父鱼鳃中存在顶端和亚顶端的Na⁺/H⁺交换体2（NHE2）。NHE2存在于大的卵形氯化物细胞中，并且经常与Na⁺/K⁺-ATP酶共定位于同一细胞中。我们还检测到V-H⁺-ATP酶免疫反应性，主要存在于鳃小片基部的细胞中，染色模式表明其位于基底外侧。用抗NHE2抗体在免疫印迹上检测到的85 kDa蛋白在对照动物和酸注入动物中均有发现，并且在8小时的大急性酸中毒后没有变化。
