Zimmer Alex M, Wilson Jonathan M, Wright Patricia A, Hiroi Junya, Wood Chris M
Department of Biology, University of Ottawa, Ottawa, ON, Canada K1N 6N57
Department of Biology, Wilfrid Laurier University, ON, Canada N2L 3C5.
J Exp Biol. 2017 Mar 1;220(Pt 5):775-786. doi: 10.1242/jeb.148429. Epub 2016 Dec 13.
In rainbow trout, the dominant site of Na uptake () and ammonia excretion () shifts from the skin to the gills over development. Post-hatch (PH; 7 days post-hatch) larvae utilize the yolk sac skin for physiological exchange, whereas by complete yolk sac absorption (CYA; 30 days post-hatch), the gill is the dominant site. At the gills, and occur via loose Na/NH exchange, but this exchange has not been examined in the skin of larval trout. Based on previous work, we hypothesized that, contrary to the gill model, by the yolk sac skin of PH trout occurs independently of Following a 12 h exposure to high environmental ammonia (HEA; 0.5 mmol l NHHCO; 600 µmol l Na; pH 8), by the gills of CYA trout and the yolk sac skin of PH larvae, which were isolated using divided chambers, increased significantly. However, this was coupled to an increase in across the gills only, supporting our hypothesis. Moreover, gene expression of proteins involved in [Na/H-exchanger-2 (NHE2) and H-ATPase] increased in response to HEA only in the CYA gills. We further identified expression of the apical Rhesus (Rh) proteins Rhcg2 in putative pavement cells and Rhcg1 (co-localized with apical NHE2 and NHE3b and Na/K-ATPase) in putative peanut lectin agglutinin-positive (PNA) ionocytes in gill sections. Similar Na/K-ATPase-positive cells expressing Rhcg1 and NHE3b, but not NHE2, were identified in the yolk sac epithelium. Overall, our findings suggest that the mechanisms of and by the dominant exchange epithelium at two distinct stages of early development are fundamentally different.
在虹鳟鱼中，钠摄取（）和氨排泄（）的主要部位在发育过程中从皮肤转移到鳃。孵化后（PH；孵化后7天）的幼体利用卵黄囊皮肤进行生理交换，而到卵黄囊完全吸收时（CYA；孵化后30天），鳃成为主要部位。在鳃中，和通过松散的钠/氨交换发生，但这种交换尚未在幼体虹鳟鱼的皮肤中进行研究。基于之前的工作，我们假设，与鳃模型相反，PH虹鳟鱼卵黄囊皮肤的发生独立于。在暴露于高环境氨（HEA；0.5 mmol·l NHHCO；600 μmol·l Na；pH 8）12小时后，使用分隔室分离的CYA虹鳟鱼的鳃和PH幼体的卵黄囊皮肤的显著增加。然而，这仅与鳃中 的增加相关，支持了我们的假设。此外，仅在CYA鳃中，参与 [钠/氢交换器-2（NHE2）和氢-ATP酶] 的蛋白质的基因表达响应HEA而增加。我们进一步在鳃切片中推定的扁平细胞中鉴定了顶端恒河猴（Rh）蛋白Rhcg2的表达，以及在推定的花生凝集素阳性（PNA）离子细胞中Rhcg1（与顶端NHE2和NHE3b以及钠/钾-ATP酶共定位）的表达。在卵黄囊上皮中鉴定出表达Rhcg1和NHE3b但不表达NHE2的类似钠/钾-ATP酶阳性细胞。总体而言，我们的研究结果表明，早期发育两个不同阶段的主要交换上皮的和机制存在根本差异。
