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Branchial NH 4 + ‐dependent Acid‐base Transport Mechanisms and Energy Metabolism of Squid ( Sepioteuthis lessoniana ) Affected by Seawater Acidification
Author(s) -
Sung PoHsuan,
Chen YuChi,
Lee JayRon,
Hu Marian,
Hwang PungPung,
Tseng YungChe
Publication year - 2015
Publication title -
the faseb journal
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.709
H-Index - 277
eISSN - 1530-6860
pISSN - 0892-6638
DOI - 10.1096/fasebj.29.1_supplement.843.2
Subject(s) - cotransporter , extracellular , seawater , biochemistry , cuttlefish , carbonic anhydrase , ocean acidification , biology , biophysics , atpase , intracellular ph , metabolism , acid–base homeostasis , chemistry , microbiology and biotechnology , sodium , enzyme , ecology , fishery , organic chemistry
CO 2 induced pH fluctuation in the extracellular compartments are a unifying physiological phenomenon that all animals are confronted with. Cephalopods have evolved acid‐base regulatory abilities to accommodate temporal pH fluctuations via highly pH sensitive hemocyanins. Interestingly, it has been suggested that metabolic energetic limitations may be a critical factor when exposed to acidified seawater. Here we show the effects of short‐term (few hours) to medium‐term (up to 168 h) seawater acidification on pelagic squids, Sepioteuthis lessoniana . Routine metabolic rates, NH 4 + secretion and extracellular acid‐base balance were monitored during exposure to control (pH 8.1) and acidified conditions of pH 7.7 and 7.3 along a period of 168h. Metabolic rates were significantly depressed by 40% after 168 hours in pH 7.3 conditions exposure. The extracellular pH is fully restored within 20 h and is maintained along the period of 168 h, and the accompanied acid‐base transporter transcripts were up‐regulated including V‐type H + ‐ATPase (VHA), Rhesus protein (RhP), Na/HCO 3 ‐ cotransporter (NBC) and cystolic carbonic anhydrase (CAc). Immunohistochemical analyses demonstrated co‐localization of Na + /K + ‐ATPase (NKA), VHA in basolateral and Na + /H + ‐exchanger 3 (NHE3), RhP in apical membranes of the branchial epithelium. Protein levels of branchial VHA and RhP were increased in response to acidified conditions. The present work demonstrated the NH 4 + based proton secretion via RhP may contribute to a well‐developed acid‐base regulatory machinery in branchial epithelia of cephalopods.