Expression of aquaporin 3 in gills of the Atlantic killifish (Fundulus heteroclitus): Effects of seawater acclimation

Abstract

Estuarine fish, such as the Atlantic killifish (Fundulus heteroclitus), are constantly and rapidly exposed to changes in salinity. Although ion transport in killifish gills during acclimation to increased salinity has been studied extensively, no studies have examined the role of aquaglyceroporin 3 (AQP3), a water, glycerol, urea, and ammonia transporter, during acclimation to increased salinity in this sentinel environmental model organism. The goal of this study was to test the hypothesis that transfer from freshwater to seawater decreases AQP3 gene and protein expression in the gill of killifish. Transfer from freshwater to seawater decreased AQP3 mRNA in the gill after 1 day, but had no effect on total gill AQP3 protein abundance as determined by western blot. Quantitative confocal immunocytochemistry confirmed western blot studies that transfer from freshwater to seawater did not change total AQP3 abundance in the gill; however, immunocytochemistry revealed that the amount of AQP3 in pillar cells of secondary lamellae decreased in seawater fish, whereas the amount of AQP3 in mitochondrion rich cells (MRC) in primary filaments of the gill increased in seawater fish. This response of AQP3 expression is unique to killifish compared to other teleosts. Although the role of AQP3 in the gill of killifish has not been completely elucidated, these results suggest that AQP3 may play an important role in the ability of killifish to acclimate to increased salinity.

Reciprocal osmotic challenges reveal mechanisms of divergence in phenotypic plasticity in the killifish Fundulus heteroclitus

“…BW-native fish again trend towards a return to control expression levels in the hyper-osmotic challenge while expression in the FW-native fish did not recover to control levels. Similar responses of AQP3 have been observed in previous studies of F. heteroclitus (Jung et al, 2012;Whitehead et al, 2012b), as well as other species of killifish (Kozak et al, 2014;Whitehead et al, 2013). Together with regulation of VCAN, these data suggest divergence in RVI and RVD responses between the BW-native and FW-native populations.…”

Hormonal regulation of aquaporin 3: opposing actions of prolactin and cortisol in tilapia gill

“…Multiple investigators have approached this question by localizing Aqp3 protein in gill tissue. In eel (Anguilla anguilla), killifish (Fundulus heteroclitus), and rainbow wrasse (Coris julis), Aqp3 immunoreactivity was observed in basolateral membrane of ionocytes (Lignot et al 2002, Brunelli et al 2010, Jung et al 2012. Here, we observed extensive Aqp3 immunoreactivity in ionocytes, mucous cells, and pavement cells of the afferent-vascular edges of FW filaments (Fig.…”

“…We and others have shown that branchial aqp3 expression in teleosts is rapidly modulated in response to changes in salinity, with elevated expression in FW versus SW , Lignot et al 2002, Tse et al 2006, Tipsmark et al 2010, Whitehead et al 2010, Jung et al 2012, Lam et al 2014, Madsen et al 2014, Moorman et al 2015. Prl has long been recognized as "the FW-adapting hormone" in fishes based upon its capacity to support branchial processes essential to life in FW (Hirano 1986, McCormick 2001.…”

“…Multiple teleost Aqps are expressed in osmoregulatory epithelia; for example, Aqp3, an aquaglyceroporin, which transports water, glycerol, and urea, has been studied in a suite of euryhaline teleosts with particular attention to its expression following changes in salinity. In surveyed species, branchial aqp3 gene expression is markedly elevated in FW-versus SW-acclimated animals , Lignot et al 2002, Tse et al 2006, Tipsmark et al 2010, Whitehead et al 2010, Jung et al 2012, Madsen et al 2014, Moorman et al 2015. Although the functional significance of plastic aqp3 expression in the gill stands unresolved, regulated transepithelial water movement, via Aqp3, appears unlikely on the basis that branchial water exchange is disadvantageous for fish in both FW and SW environments (Cerdà & Finn 2010).…”

Evaluation of the Estrogenic and Osmoregulatory Impacts Of Exposure to 4-Nonylphenol Pollution in the Estuarine Arrow Goby, Clevelandia Ios

“…While the gene expression changes that enable this equalization occur more than 24 hrs after salinity transfer, the expression of core transporters such as Aqp3, Cftr, and subunits of NKA are upregulated more rapidly (McCormick et al, 2013). For instance, in the mummichog, mRNAs encoding aqp3 were observed to increase in abundance within 6 hrs of beginning a low salinity challenge (Jung et al, 2012).…”