Differential Expression and Localization of Branchial AQP1 and AQP3 in Japanese Medaka (Oryzias latipes)

Abstract

Aquaporins (AQPs) facilitate transmembrane water and solute transport, and in addition to contributing to transepithelial water transport, they safeguard cell volume homeostasis. This study examined the expression and localization of AQP1 and AQP3 in the gills of Japanese medaka (Oryzias latipes) in response to osmotic challenges and osmoregulatory hormones, cortisol, and prolactin (PRL). AQP3 mRNA was inversely regulated in response to salinity with high levels in ion-poor water (IPW), intermediate levels in freshwater (FW), and low levels in seawater (SW). AQP3 protein levels decreased upon SW acclimation. By comparison, AQP1 expression was unaffected by salinity. In ex vivo gill incubation experiments, AQP3 mRNA was stimulated by PRL in a time- and dose-dependent manner but was unaffected by cortisol. In contrast, AQP1 was unaffected by both PRL and cortisol. Confocal microscopy revealed that AQP3 was abundant in the periphery of gill filament epithelial cells and co-localized at low intensity with Na+,K+-ATPase in ionocytes. AQP1 was present at a very low intensity in most filament epithelial cells and red blood cells. No epithelial cells in the gill lamellae showed immunoreactivity to AQP3 or AQP1. We suggest that both AQPs contribute to cellular volume regulation in the gill epithelium and that AQP3 is particularly important under hypo-osmotic conditions, while expression of AQP1 is constitutive.

Transcriptome analysis reveals the high temperature induced damage is a significant factor affecting the osmotic function of gill tissue in Siberian sturgeon (Acipenser baerii)

“…8 B). It has been demonstrated that the gill tissue improves active ion absorption capacity and resists ion loss by increasing the expression levels of NHE3 , CLC-2 , and AE2, when fishes migrate from high-salt environment to freshwater [ 15 , 47 – 49 ]. Numerous previous studies have shown that NKA-α expression decreases when water temperature increases [ 22 , 50 , 51 ], this was substantiated by the change results of heat stress at 28℃ and 24℃ when compared to 20℃ in our study (Fig.…”

Morphological and Functional Alterations Induced by Two Ecologically Relevant Concentrations of Lead on Danio rerio Gills

“…Exposure to lead and other heavy metals induces osmoregulatory dysfunctions that are recognized as the main toxicity mechanisms of these pollutants in seawater and freshwater fish [ 20 , 29 , 60 , 61 ]. In basal conditions, Na + /K + -ATPase and aquaporin-3 (AQP3) are widely expressed within this key osmoregulatory organ and localize in the basolateral membrane of chloride cells (CCs), where they mediate the movements of water and selected ions between intracellular and extracellular fluids [ 42 , 43 ]. CCs are often a target of heavy metals’ toxicity [ 62 ], and in situations that prevent their normal function, the gills might promote their differentiation to increase ions uptake [ 62 , 63 ].…”

“…Therefore, to evaluate the functional disorders under experimental conditions, we used a real-time PCR (RT-PCR) to detect and quantify key enzymes correlated to specific Pb toxicity pathways in zebrafish gills in a second step. Na + /K + -ATPase and aquaporin-3 (AQP3) are expressed within key osmoregulatory tissues where they mediate the active transmembrane movement of water and selected ions between intracellular and extracellular fluids [ 42 , 43 ] and are widely recognized as valuable biomarkers in xenobiotics-induced osmotic stress [ 24 , 26 , 29 , 44 , 45 ]. In fish, protective pathways are activated to regulate heavy metal ions and prevent tissue damage [ 46 , 47 ], including metallothioneins (MTs) induction.…”

Global assessment of the response to chronic stress in European sea bass

“…However, several studies suggest that aqp3 and ncc2a are also implicated in gill functions since SW adapted fish show significant levels of the transcripts (Blondeau-Bidet et al, 2019a;Breves et al, 2020;Giffard-Mena et al, 2007;Jung et al, 2012;Moorman et al, 2015;Tipsmark et al, 2010). Aqp3 immunoreactivity appears quantitatively similar whatever the salinity in medaka (Ellis et al, 2019) and protein abundance does not change significantly in killifish (Jung et al, 2012). Ncc2 protein was also quantified in SW-acclimated mummichogs using western blot approach (Breves et al, 2020).…”