Mechanism of acid adaptation of a fish living in a pH 3.5 lake

Abstract

Despite unfavorable conditions, a single species of fish, Osorezan dace, lives in an extremely acidic lake (pH 3.5) in Osorezan, Aomori, Japan. Physiological studies have established that this fish is able to prevent acidification of its plasma and loss of Na(+). Here we show that these abilities are mainly attributable to the chloride cells of the gill, which are arranged in a follicular structure and contain high concentrations of Na(+)-K(+)-ATPase, carbonic anhydrase II, type 3 Na(+)/H(+) exchanger (NHE3), type 1 Na(+)-HCO(3)(-) cotransporter, and aquaporin-3, all of which are upregulated on acidification. Immunohistochemistry established their chloride cell localization, with NHE3 at the apical surface and the others localized to the basolateral membrane. These results suggest a mechanism by which Osorezan dace adapts to its acidic environment. Most likely, NHE3 on the apical side excretes H(+) in exchange for Na(+), whereas the electrogenic type 1 Na(+)-HCO(3)(-) cotransporter in the basolateral membrane provides HCO(3)(-) for neutralization of plasma using the driving force generated by Na(+)-K(+)-ATPase and carbonic anhydrase II. Increased expression of glutamate dehydrogenase was also observed in various tissues of acid-adapted dace, suggesting a significant role of ammonia and bicarbonate generated by glutamine catabolism.

Background adaptation and water acidification affect pigmentation and stress physiology of tilapia, Oreochromis mossambicus

“…Plasma pH values between 7.3 and 7.5 have been reported to be normal values in fish (Hirata et al, 2003), which correspond well with the values found in our study. A two-day decrease of water pH was not experienced as stressful in the present study as indicated by the lack of a significant rise in plasma pH and cortisol levels, which is in line with previous reports (Ginneken et al, 1997;Lamers et al, 1994), in which either a 6h or a 24h period of gradual water acidification was applied.…”

Differential expression of Na+-Cl−cotransporter and Na+-K+-Cl−cotransporter 2 in the distal nephrons of euryhaline and seawater pufferfishes

“…1), and the conventional NCC was not markedly expressed in the gill (Fig. 2) (11,16,54), suggesting that a NCC-independent mechanism is operating in the gills of freshwater mefugu to absorb sodium ions; one possibility involves NHE3, as previously proposed by this group, Choe et al, and Yan et al for the Osorezan dace (20), Atlantic stingray (8), and zebrafish (57), respectively. Future studies will focus on the regulatory mechanisms that govern NCC and NKCC2 gene expression and how the various nephron segments are formed.…”

Ion uptake and acid secretion in zebrafish (Danio rerio)

“…NBC1 has been immunocytochemically identified in gill ionocytes of Osorezan dace (Tribolodon hakonensis) (Hirata et al, 2003) and rainbow trout (Parks et al, 2007). In a study on isolated rainbow trout gill PNA -cells (Parks et al, 2007), electrogenic NBC activity was supported by DIDS (an NBC inhibitor)-sensitive, Na + -induced membrane potential depolarization as observed via imaging of the voltage-sensitive dye bis-oxonol.…”