A carrier enzyme basis for ammonium excretion in teleost gill. NH+4-stimulated Na-dependent ATPase activity in Opsanus beta

Rh glycoprotein expression is modulated in pufferfish (Takifugu rubripes) during high environmental ammonia exposure

“…In the current study, NKA clearly responded to HEA in the pufferfish gills. NKA mRNA expression and activity were significantly elevated after exposure to 48h of NH 4 HCO 3 (Figs4 and 11), and, furthermore, we have demonstrated that NH 4 + was a functional substrate, capable of activating the enzyme in the absence of K + (Fig.11), as was previously demonstrated with toadfish and mudskipper gill NKA (Mallery, 1983;Randall et al, 1999). Although there was a delay between the transcription and translation of NKA after 12h exposure to 5mmoll -1 NH 4 HCO 3 (Table3, Fig.8), mRNA and protein levels were both upregulated after 48h of exposure to 1mmoll -1 NH 4 HCO 3 (Figs4 and 8).…”

“…NKA has been implicated in the basolateral uptake of ammonia in the collecting duct of the mammalian kidney (Kurtz and Balaban, 1986;Wall and Koger, 1994) and similarly, basolateral gill Na + /NH 4 + exchange via NKA has been suggested from studies on the toadfish (Claiborne et al, 1982;Mallery, 1983). In fact, active excretion of ammonia against a gradient via NKA was demonstrated in mudskippers exposed to HEA (Randall et al, 1999).…”

An animal homolog of plant Mep/Amt transporters promotes ammonia excretion by the anal papillae of the disease vector mosquito,Aedes aegypti

“…First, NKA may transport ammonia as NH 4 + , which competes with K + or where there are separate binding sites for these two ions (Skou, 1960;Masui et al, 2002;Cruz et al, 2013). There is considerable evidence for this ammonia transport mechanism in a number of animal epithelia, such as crab gills and the antennal gland (see Weihrauch et al, 2004, for review), frog skin (Cruz et al, 2013), fish gills (Mallery, 1983), the epidermis of planaria (Weihrauch et al, 2012b) and potentially larval zebrafish skin (see Shih et al, 2013). Second, as NKA is co-localized with AeAmt1 on the basal side, it can provide a strong voltage gradient to drive NH 4 + through AeAmt1 from the hemolymph to the cytosol.…”

Ammonia excretion inCaenorhabditis elegans: mechanism and evidence of ammonia transport of the Rhesus protein CeRhr-1

“…For the basolateral localized Na + /K + -ATPase, it was shown in 1960 by Jens Skou that this enzyme does accept NH 4 + as a substrate by replacing K + ions (Skou, 1960) and thereby is capable of actively pumping NH 4 + from the body fluids into the respective ammonia-transporting epithelial cell. The direct participation of this pump in the ammonia transport mechanism has now been identified for numerous systems, including those in gills of crustaceans (Furriel et al, 2004;Masui et al, 2002;Weihrauch et al, 1998;Weihrauch et al, 1999) and fish (Mallery, 1983;Nawata et al, 2010a;Wood et al, 2013), frog skin (Cruz et al, 2013), mammalian kidney (Garvin et al, 1985;Wall and Koger, 1994) and intestine (Worrell et al, 2008). The second pump often, if not always, involved in the ammonia transport processes is the V-ATPase.…”