Maintenance of sodium ion balance in rainbow trout exposed to moderately acidic water is achieved through reduction of sodium efflux

In most freshwater fishes, exposure to acidic water decreases rates of active ion uptake and increases rates of passive ion efflux. To survive in low pH conditions, fish must possess mechanisms to maintain net ion flux rates close to zero. In this study, rainbow trout (Oncorhynchus mykiss) exposed to moderate acidity (pH = 4.5 or 5.5) in hard water demonstrated Na+ influx inhibition relative to fish held in control conditions (pH = 8.0). However, Na+ efflux rates were significantly lower in fish exposed to low pH, which minimized the net loss of Na+. This represents a relatively novel mechanism utilized by an acid sensitive species to maintain ion balance in low pH and appeared to be a result of reduced gill paracellular permeability, though we did not observe any significant differences in the transcript abundance of 6 different tight junction genes in response to low pH exposure. Overall, we conclude that acid tolerance may be dictated by differences in efflux rates in fishes that, li..., , , # Maintenance of sodium ion balance in rainbow trout exposed to moderately acidic water is achieved through reduction of sodium efflux

acid_trout.csv

\[Access this dataset on Dryad]([https://doi.org/10.5061/dryad.sf7m0cggn](https://doi.org/10.5061/dryad.sf7m0cggn))

Dataset in \"acid_trout.csv\" contains data presented in figures 1, 2, 3, and 5, and also includes mass for each fish (see below for unit descriptions for the presented data).

Data in rows 2 to 85 were obtained in Experimental Series 1 [fish_id = [1, 84]

Data in rows 86-121 were collected in Experimental Series 2 [fish_id = [113, 148]

Data in rows 122-156 were collected in Experimental Series 3 [fish_id = [157, 192]

Description of the data and file structure for \"acid_trout.csv\"

Column labels:

fish_id = Fish ID used to organize multiple endpoints measured in the same fish (e.g. Series 1 and 3)

ph = pH treatment

time = duration of the pH exposure (h)

sodium_influx = Na+ influx (umol/g/h); presented in Fig. 1A; empty ...,