銀離子對廣鹽性青鱂魚胚胎離子調節與海水適應能力之影響
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2022
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銀被廣泛應用於商業產品與醫療器材中，例如：抗菌劑、個人護理產品、傷口的敷料……等。隨著銀的廣泛使用，此類化學物質對水生環境的潛在負面影響也日漸受到重視。過去文獻指出，銀離子暴露會干擾魚類離子調節的功能、損害魚類的肝臟、鰓、腸子等器官與造成胚胎發育毒性，但針對銀是否會影響廣鹽性魚類適應環境鹽度轉變的能力，相關研究較為少見。本研究利用青鱂魚（Oryzias latipes）胚胎作為模式動物，更全面性地探討銀離子在淡水與海水中對廣鹽性魚類離子與滲透壓調節的影響。硝酸銀暴露7天後，淡水與海水馴養組的半致死濃度分別為0.17 ppm與1.01ppm。淡水馴養組的胚胎心率顯著上升、以NKA免疫細胞螢光染色標定的離子細胞密度顯著下降，而海水處理組則是沒有顯著變化。將胚胎暴露於含有硝酸銀的海水8天後，發現胚胎的相對喝水量顯著下降、腸道細胞的凋亡程度顯著上升，還可觀察到腸道組織與上皮細胞受損。將胚胎暴露於含有硝酸銀（0.01、0.05、0.1 ppm）的淡水7天後，轉移至含有相同硝酸銀濃度的海水中12小時，並評估銀離子對胚胎的海水適應能力之影響。結果顯示，胚胎的死亡率顯著上升、心率顯著下降，形態方面則觀察到體軸彎曲、軀幹脫水與圍心腔水腫。離子調節方面，以NKA免疫系標染色所標定的離子細胞形態變形且細胞密度顯著下降、以MitoTracker標定的卵黃囊上具粒線體活性的離子細胞之細胞密度下降、頂膜開口的大小沒有產生適應性變化，顯示離子細胞受損且可能無法轉為海水型。此外，硝酸銀暴露還會使胚胎轉移至海水後的相對喝水量顯著下降。由於離子與滲透壓調節器官的功能受損，最後導致胚胎體內鈉離子含量顯著上升。綜合以上結果，可知銀離子毒性在淡水環境下比海水環境下強，且在淡水中會造成卵黃囊上的離子細胞損傷，而在海水中則會造成腸道組織與細胞受損並降低吸收水分的能力。當離子與滲透壓調節器官受影響時，胚胎亦無法成功適應環境鹽度的改變。
Silver is widely used in commercial products and medical devices, such as antibacterial agents, personal care products, wound dressings. With the increasing use of silver, concerns about their potential risk on aquatic ecosystems have increased. Several studies have demonstrated that silver interferes with ionregulatory functions, caused damages to the liver, gill, and intestine, and leads to developmental defects. However, little is known about the toxic effects of Ag+ on the ability of euryhaline fish to adapt to the environmental salinity changes. In this study, medaka (Oryzias latipes) embryos were used as an animal model to investigate the effect of silver on the ion regulation and osmoregulation of euryhaline fish in both freshwater (FW) and seawater (SW). After being exposed to AgNO3 for 7 days, the LC50 was calculated to be 0.17 and 1.01 ppm in FW and SW, respectively. Moreover, the heart rate significantly increased and the density of ionocytes significantly decreased after AgNO3 exposure in FW, while there was no significant difference between the SW acclimation groups. Furthermore, after being exposed to AgNO3 for 8 days in SW, it was found that the relative drinking rates significantly decreased, the degree of apoptosis of intestinal cells was significantly increased, and damages to intestinal tissues and epithelial cells were also observed. The embryos were exposed to AgNO3 in FW for 7 days and then transferred to SW containing the same concentration of AgNO3 for 12 hours to assess the effect of Ag+ on the seawater adaptation. The results showed that the mortality significantly increased and the heart rate significantly decreased. Also, Ag+ caused malformations after the embryos transferred to SW, including bending of the body axis, dehydration of the trunk, and pericardial edema were observed. Besides, it was found that the ionocytes density significantly decreased and the morphology was deformed (indicated by NKA immunocytochemistry). The mitochondrial activity of ionocytes was significantly decreased (indicated by MitoTracker staining). Moreover, there were no adaptive changes in the size of the apical opening of ionocytes. These results indicated that the ionocytes were damaged and may not be able to convert to seawater type. In addition, Ag+ can also cause a decrease in the relative drinking rates after being transferred. Due to the impaired function of the ionregulatory and osmoregulatory organs, the sodium ion content eventually significantly increased. In conclusion, the toxicity of Ag+ is stronger in FW than in SW. In FW, Ag+ caused damages to ionocytes on the yolk sac, while in SW, it caused damages to intestinal tissues and cells and reduced the ability to absorb water. When the ionregulatory and osmoregulatory organs were affected, the embryos cannot successfully adapt to the changes in environmental salinity.
Silver is widely used in commercial products and medical devices, such as antibacterial agents, personal care products, wound dressings. With the increasing use of silver, concerns about their potential risk on aquatic ecosystems have increased. Several studies have demonstrated that silver interferes with ionregulatory functions, caused damages to the liver, gill, and intestine, and leads to developmental defects. However, little is known about the toxic effects of Ag+ on the ability of euryhaline fish to adapt to the environmental salinity changes. In this study, medaka (Oryzias latipes) embryos were used as an animal model to investigate the effect of silver on the ion regulation and osmoregulation of euryhaline fish in both freshwater (FW) and seawater (SW). After being exposed to AgNO3 for 7 days, the LC50 was calculated to be 0.17 and 1.01 ppm in FW and SW, respectively. Moreover, the heart rate significantly increased and the density of ionocytes significantly decreased after AgNO3 exposure in FW, while there was no significant difference between the SW acclimation groups. Furthermore, after being exposed to AgNO3 for 8 days in SW, it was found that the relative drinking rates significantly decreased, the degree of apoptosis of intestinal cells was significantly increased, and damages to intestinal tissues and epithelial cells were also observed. The embryos were exposed to AgNO3 in FW for 7 days and then transferred to SW containing the same concentration of AgNO3 for 12 hours to assess the effect of Ag+ on the seawater adaptation. The results showed that the mortality significantly increased and the heart rate significantly decreased. Also, Ag+ caused malformations after the embryos transferred to SW, including bending of the body axis, dehydration of the trunk, and pericardial edema were observed. Besides, it was found that the ionocytes density significantly decreased and the morphology was deformed (indicated by NKA immunocytochemistry). The mitochondrial activity of ionocytes was significantly decreased (indicated by MitoTracker staining). Moreover, there were no adaptive changes in the size of the apical opening of ionocytes. These results indicated that the ionocytes were damaged and may not be able to convert to seawater type. In addition, Ag+ can also cause a decrease in the relative drinking rates after being transferred. Due to the impaired function of the ionregulatory and osmoregulatory organs, the sodium ion content eventually significantly increased. In conclusion, the toxicity of Ag+ is stronger in FW than in SW. In FW, Ag+ caused damages to ionocytes on the yolk sac, while in SW, it caused damages to intestinal tissues and cells and reduced the ability to absorb water. When the ionregulatory and osmoregulatory organs were affected, the embryos cannot successfully adapt to the changes in environmental salinity.
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銀離子, 青鱂魚, 離子細胞, 離子調節, 滲透壓調節, 鹽度挑戰, silver ion, medaka, ionocyte, ionregulation, osmoregulation, salinity challenge