Rapid blood acid-base regulation by European sea bass (Dicentrarchus labrax) in response to sudden exposure to high environmental CO2.
J Exp Biol
; 225(2)2022 01 15.
Article
em En
| MEDLINE
| ID: mdl-35005768
ABSTRACT
Fish in coastal ecosystems can be exposed to acute variations in CO2 of between 0.2 and 1â
kPa CO2 (2000-10,000â
µatm). Coping with this environmental challenge will depend on the ability to rapidly compensate for the internal acid-base disturbance caused by sudden exposure to high environmental CO2 (blood and tissue acidosis); however, studies about the speed of acid-base regulatory responses in marine fish are scarce. We observed that upon sudden exposure to â¼1â
kPa CO2, European sea bass (Dicentrarchus labrax) completely regulate erythrocyte intracellular pH within â¼40â
min, thus restoring haemoglobin-O2 affinity to pre-exposure levels. Moreover, blood pH returned to normal levels within â¼2â
h, which is one of the fastest acid-base recoveries documented in any fish. This was achieved via a large upregulation of net acid excretion and accumulation of HCO3- in blood, which increased from â¼4 to â¼22â
mmolâ
l-1. While the abundance and intracellular localisation of gill Na+/K+-ATPase (NKA) and Na+/H+ exchanger 3 (NHE3) remained unchanged, the apical surface area of acid-excreting gill ionocytes doubled. This constitutes a novel mechanism for rapidly increasing acid excretion during sudden blood acidosis. Rapid acid-base regulation was completely prevented when the same high CO2 exposure occurred in seawater with experimentally reduced HCO3- and pH, probably because reduced environmental pH inhibited gill H+ excretion via NHE3. The rapid and robust acid-base regulatory responses identified will enable European sea bass to maintain physiological performance during large and sudden CO2 fluctuations that naturally occur in coastal environments.
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MEDLINE
Assunto principal:
Bass
Limite:
Animals
Idioma:
En
Revista:
J Exp Biol
Ano de publicação:
2022
Tipo de documento:
Article