Branchial osmoregulation in the euryhaline bull shark, Carcharhinus leucas: a molecular analysis of ion transporters

Abstract

SUMMARYBull sharks, Carcharhinus leucas, are one of only a few species of elasmobranchs that live in both marine and freshwater environments. Osmoregulation in euryhaline elasmobranchs is achieved through the control and integration of various organs (kidney, rectal gland and liver) in response to changes in environmental salinity. However, little is known regarding the mechanisms of ion transport in the gills of euryhaline elasmobranchs and how they are affected by osmoregulatory challenges. This study was conducted to gain insight into the branchial ion and acid-base regulatory mechanisms of C. leucas by identifying putative ion transporters and determining whether their expression is influenced by environmental salinity. We hypothesised that expression levels of the Na

Physiological and molecular responses of the spiny dogfish shark (Squalus acanthias) to high environmental ammonia: scavenging for nitrogen

“…2) located, in contrast to teleosts. Instead, all current models for the elasmobranch gill indicate that H + -ATPase functions basolaterally in those ionocytes, which excrete base (Piermarini and Evans, 2001;Piermarini et al, 2002;Tresguerres et al, 2005;Reilly et al, 2011), so that H + ions are returned to the blood when HCO 3 -is excreted apically at times of blood alkalosis (Tresguerres et al, 2005;Tresguerres et al, 2006;Tresguerres et al, 2007;Roa et al, 2014). In the present study, there was a slight tendency towards alkalosis during HEA exposure, with a significant rise in plasma [HCO 3 -] (Fig.…”

Living with a leaky skin: upregulation of ion transport proteins during sloughing

“…However, the I sc (the likelihood of the number of channels opened at a particular time) alone cannot determine the functional activity of ENaC, as the open probability is highly variable depending on external factors (Anantharam et al, 2006;Kleyman et al, 2009); thus, measuring amiloride-sensitive I sc can quantify the functional activity of ENaC (Sariban-Sohraby and Benos, 1986). In addition, an increase in subunit abundance does not always indicate an increase in functional activity of the whole protein (Sardella and Kültz, 2009;Reilly et al, 2011). For example, the ENaC subunits (α-, β-and γ-subunits) alone cannot induce amiloride-sensitive currents (Canessa et al, 1994), and in bullfrog (Rana catesbeiana) tadpoles, ENaC is expressed in the skin but not in a functional state (no amiloride-blockable Na + transport present) until metamorphosis (Takada et al, 2006).…”

Novel and potential physiological roles of vacuolar-type H+-ATPase in marine organisms

“…The gills of teleost fishes also have several cell subtypes, and serve a dual purpose in A/B regulation and NaCl transport for osmoregulation (Evans et al, 2005). Elasmobranch gills contain two types of specialized acid-and base-secreting cells that regulate the blood A/B status (Piermarini and Evans, 2001;Reilly et al, 2011;Roa et al, 2014;Tresguerres et al, 2005). Base-secreting cells are 'VHA-rich', express abundant intracellular CA (Tresguerres et al, 2007b) and apical pendrin-like (see Glossary) anion exchangers (Piermarini et al, 2002;Reilly et al, 2011;Roa et al, 2014), and are mitochondrion-rich .…”

“…Elasmobranch gills contain two types of specialized acid-and base-secreting cells that regulate the blood A/B status (Piermarini and Evans, 2001;Reilly et al, 2011;Roa et al, 2014;Tresguerres et al, 2005). Base-secreting cells are 'VHA-rich', express abundant intracellular CA (Tresguerres et al, 2007b) and apical pendrin-like (see Glossary) anion exchangers (Piermarini et al, 2002;Reilly et al, 2011;Roa et al, 2014), and are mitochondrion-rich . Normally, fish metabolism is net acidic because of CO 2 release from mitochondria, H + derived from anaerobic glycolysis and NH 4 + resulting from amino acid catabolism.…”