神經內分泌胜肽趨同調控虎斑烏賊體液酸鹼恆定之探討
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2016
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頭足類動物與硬骨魚類的胚胎對於調控體液酸鹼平衡的模式具有相似性，然而在頭足類動物上，這種生理現象於演化發育上的分子調控機制所知仍有限。本研究運用虎斑烏賊(Sepia pharaonis)的胚胎進行高碳酸的環境刺激，探測催產素同源基因sepiatocin、pro-sepiatocin及其受器sepiatocin-related receptor (spr)的表現，並檢測虎斑烏賊的耐酸能力。研究結果發現：虎斑烏賊的胚胎於不同發育時期能忍受不同程度的碳酸壓力，最低可至pH7.0。而藉由原位雜合分析亦發現spr會表現在虎斑烏賊胚胎的表皮及鰓上，sepiatocin及pro-sepiatocin和zn12標記的神經細胞有共定位的表現，顯示頭足類由神經細胞分泌sepiatocin及pro-sepiatocin。此外，高碳酸的壓力一方面會於不同的時間點顯著刺激pro-sepiatocin、sepiatocin與spr的表現，同時也影響虎斑烏賊胚胎表皮的離子調節蛋白(vha、nbc、nhe3、rhp、nhe3)及p63的基因表現，顯示與sepiatocin相關的激素可能參與體液酸鹼恆定，而頭足類胚胎與硬骨魚胚胎的酸鹼調控機制與表皮調控路徑的相似性應為在生存競爭下，兩者生理機制趨向趨同演化的證據之一。
Cephalopods were proved to process epithelial acid-base regulatory machinery; however, its evo-devo bases for extracellular pH homeostasis are still poorly understood. In this study, we used embryos of cuttlefish, Sepia pharaonis, to examine integrative expressions of, neurohypophysial hormones (pro-sepiatocin and sepiatocin) and its possible receptor (sepiatocin-related receptor, spr) under CO2-induced acidification. Intact resting respiration data showed that S. pharaonis embryos, whose gills were well developed in stage 24 and stage 28, were capable of surviving under CO2 perturbations as low as to pH7.6 and pH7.0, respectively. In addition, RNA in situ hybridization images indicated that spr2 were expressed in embryonic epithelium and adult gills, the dominant sites for acid-base regulation and pro-sepiatocin and sepiatocin were expressed on the optic lobes. Sepiatocin related genes were found to be upregulated accompanied with those stimulated genes for epithelial acid-base regulation (e.g. nbc, nhe3, rhp and nka) in CO2-acidified condition; moreover, the gill perfusion proved pro-sepiatocin can directly increase the excretion of proton and ammonium. In conclusion, the present work inferred that the promptly activations of sepiatocin and spr might be involved in operating epidermal ion fluxes; accordingly, in order to cope with acid-base disturbances during their oviparous development, cephalopod embryos have evolved sophisticated evolution pathway regarding epithelium differentiation and neurohypophysial hormones regulation.
Cephalopods were proved to process epithelial acid-base regulatory machinery; however, its evo-devo bases for extracellular pH homeostasis are still poorly understood. In this study, we used embryos of cuttlefish, Sepia pharaonis, to examine integrative expressions of, neurohypophysial hormones (pro-sepiatocin and sepiatocin) and its possible receptor (sepiatocin-related receptor, spr) under CO2-induced acidification. Intact resting respiration data showed that S. pharaonis embryos, whose gills were well developed in stage 24 and stage 28, were capable of surviving under CO2 perturbations as low as to pH7.6 and pH7.0, respectively. In addition, RNA in situ hybridization images indicated that spr2 were expressed in embryonic epithelium and adult gills, the dominant sites for acid-base regulation and pro-sepiatocin and sepiatocin were expressed on the optic lobes. Sepiatocin related genes were found to be upregulated accompanied with those stimulated genes for epithelial acid-base regulation (e.g. nbc, nhe3, rhp and nka) in CO2-acidified condition; moreover, the gill perfusion proved pro-sepiatocin can directly increase the excretion of proton and ammonium. In conclusion, the present work inferred that the promptly activations of sepiatocin and spr might be involved in operating epidermal ion fluxes; accordingly, in order to cope with acid-base disturbances during their oviparous development, cephalopod embryos have evolved sophisticated evolution pathway regarding epithelium differentiation and neurohypophysial hormones regulation.
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花枝, 高碳酸, sepiatocin, pro-sepiatocin, 酸鹼調控, 趨同調控, 神經內分泌, cuttlefish, hypercapnia, sepiatocin, pro-sepiatocin, acid-base regulation, convergent capacities, neurohypophysial peptides