斑馬魚仔魚富含氫幫浦細胞對環境酸鹼值改變之短期調節機制

Abstract

魚類胚胎或仔魚必須進行酸鹼調節以應付水中酸鹼變動。斑馬魚仔魚體表上的富含氫幫浦細胞(HRCs)是主要魚體排酸的細胞。本實驗目的是探討斑馬魚仔魚排酸的短期調節機制。利用掃瞄式電子顯微鏡和共軛焦顯微鏡來觀察和量化HRCs的頂膜開口型態和密度。並利用掃瞄離子電極技術(SIET)來測量魚體內酸鹼值和魚體排出氫離子的能力。結果顯示當仔魚由pH 7轉移到pH 4環境30分鐘後，魚體內氫離子濃度有顯著增加。仔魚馴養在pH 4環境中，HRCs的頂膜開口面積和密度顯著大於馴養在pH 7環境下的仔魚。當仔魚由pH 4轉移到pH 7環境10分鐘之內，HRCs頂膜開口面積顯著下降，同時可以觀察到頂膜型態皺縮和內吞現象。然而，當仔魚由pH 7轉移到pH 4環境4小時後，HRCs頂膜開口面積才會逐漸增加。本研究證實斑馬魚仔魚具有短期調節排酸的機制。Acid-base regulation is crucial for fish to cope with environmental pH changes particularly during embryonic and larval development. H+-ATPase-rich cells (HRCs) in the skin of zebrafish larvae are the major sites for H+ secretion. In this study, I examined the short-term (in hours) regulation of H+ secretion in zebrafish subjected to ambient pH changes. Scanning electron microscopy (SEM) and confocal microscopy were used to observe and quantify the apical surface (membrane) of HRCs. Whole body pH and H+ secreting by the skin of larvae were measured with scanning ion-selective electrode technique (SIET). Results showed that whole body H+ concentration significantly increased in the larvae transferred from pH 7 to pH 4 for 30 min. The apical surface area and density of HRCs were higher in pH 4 than in pH 7 acclimated larvae. As early as 10 min after being transferred from pH 4 to pH 7, the apical surface area dramatically decreased, meanwhile morphological change and internalization of the apical surface were observed. Down-regulation of H+ secretion was also found after the transfer. In contrast, when the larvae were transferred from pH 7 to pH 4, the apical surface gradually increased after 4 h.