Manufactured titanium dioxide nanoparticles (TiO₂-NP) have been intensely applied in numerous industrial products and may be a risk for aquatic systems as they are not completely removed from domestic and industrial wastes after water treatment. This study evaluated the osmo- and ionic balance, Na⁺/K⁺-ATPase, H⁺-ATPase and carbonic anhydrase activities and the mitochondria-rich cells (MRC) in the gills and kidney of the Neotropical fish Prochilodus lineatus after 2 (acute) and 14 (subchronic) days of exposure to nominal 0, 1, 5, 10 and 50 mg L⁻¹ TiO₂-NP. The nominal concentrations corresponded to 0.0, 0.6, 1.6, 2.7 and 18.1 mg L^-1 suspended TiO₂-NP, respectively, in the water column one hour after NP introduction and were maintained for at least 24 h. Acute exposure to TiO₂-NP decreased plasma osmolality and Ca²⁺ levels. Na⁺/K⁺-ATPase, H⁺-ATPase and carbonic anhydrase activities were inhibited in the gills, but not in the kidney. Total MRC density did not change in gills and kidneys. At gill surface, total MRC density decreased in fish exposed to 50 mg L⁻¹ TiO₂-NP and the total MRC fractional surface area unchanged although, there were some changes in the fractional area of MRC with apical microvilli (MRCm) and MRC with apical sponge-like structure (MRCs). MRCm was more abundant than MRCs. After subchronic exposure, there was no change in plasma osmolality, ionic balance and enzyme activities. Total gill MRC density increased in the filament epithelium and renal tubules. In the gills, MRC contacting water exhibited some adjustments. Total MRC and fractional surface area unchanged, but there was an increase of MRCs contacting water at gill surface after exposure to10 and 50 mg L⁻¹ TiO₂-NP. MRC proliferation in filament epithelium and in renal tubules as well as the increasing MRCs at gill surface may have contributed to avoid change in plasma osmolality, ionic balance and enzyme activities and suggested a cellular physiological and morphological response to restore and maintain osmotic and ionic homeostasis after subchronic exposure.

制得的二氧化钛纳米颗粒（TiO ₂ -NP）已被广泛应用于许多工业产品中，并且由于水处理后不能从生活和工业废水中完全清除，因此可能会对水生系统构成风险。本研究评估了osmo-和离子平衡，钠⁺ / K ⁺ -ATP酶，H ⁺ -ATP酶和碳酸酐酶活动和鳃和新热带鱼的肾脏富含线粒体细胞（MRC）条纹鲮脂鲤2后（急性）和14（亚慢性）天暴露于标称0、1、5、10和50 mg L ^-1 TiO ₂ -NP。标称浓度对应于0.0、0.6、1.6、2.7和18.1 mg L ^-1NP引入后一小时，分别将TiO ₂ -NP悬浮在水柱中，并保持至少24小时。急性暴露于TiO ₂ -NP会降低血浆渗透压和Ca ²⁺含量。Na ⁺ / K ⁺ -ATPase，H ⁺ -ATPase和碳酸酐酶活性在the中被抑制，而在肾脏中则没有。M和肾脏的总MRC密度没有变化。在g表面，暴露于50 mg L ^-1 TiO ₂中的鱼的总MRC密度降低-NP和总的MRC分数表面积没有变化，尽管具有顶端微绒毛的MRC（MRCm）和具有海绵样结构的MRC（MRCs）的分数面积有一些变化。MRCm比MRCs丰富。亚慢性暴露后，血浆渗透压，离子平衡和酶活性均未改变。细丝上皮和肾小管中总g MRC密度增加。在the中，MRC接触水表现出一些调整。总MRC和部分表面积不变，但暴露于10和50 mg L ^-1 TiO ₂后，腮表面上与水接触的MRC有所增加。-NP。细丝上皮细胞和肾小管中的MRC增殖以及腮表面MRC的增加可能有助于避免血浆渗透压，离子平衡和酶活性的变化，并提示细胞生理和形态学反应可恢复和维持渗透压和离子稳态。亚慢性暴露。