title: Evidence for a plasma-accessible carbonic anhydrase in the lumen of salmon heart that may enhance oxygen delivery to the myocardium.
abstract: Oxygen supply to the heart of most teleosts, including salmonids, relies in part or in whole on oxygen-depleted venous blood. Given that plasma-accessible carbonic anhydrase (CA) in red muscle of rainbow trout has recently been shown to facilitate oxygen unloading from arterial blood under certain physiological conditions, we tested the hypothesis that plasma-accessible CA is present in the lumen of coho salmon (Oncorhynchus kisutch) hearts, and may therefore assist in the luminal oxygen supply to the spongy myocardium, which has no coronary circulation. We demonstrate a widespread distribution of CA throughout the heart chambers, including lumen-facing cells in the atrium, and confirm that the membrane-bound isoform ca4 is expressed in the atrium and ventricle of the heart. Further, we confirm that CA catalytic activity is available to blood in the atrial lumen using a modified electrometric ΔpH assay in intact atria in combination with either a membrane-impermeable CA inhibitor or specific cleavage of the Ca4 membrane anchor. Combined, these results support our hypothesis of the presence of an enhanced oxygen delivery system in the lumen of a salmonid heart, which could help support oxygen delivery when the oxygen content of venous blood becomes greatly reduced, such as after burst exercise and during environmental hypoxia.
authors.affiliation: Department of Integrative Biology, University of Guelph, Guelph, Ontario, Canada N1G 2W1 alderman@uoguelph.ca.
authors.forename: Sarah L
authors.initials: SL
authors.lastname: Alderman
authors.affiliation: Department of Zoology, University of British Columbia, Vancouver, British Columbia, Canada V6T 1Z4.
authors.forename: Till S
authors.initials: TS
authors.lastname: Harter
authors.affiliation: Department of Biology, Wilfrid Laurier University, Waterloo, Ontario, Canada N2L 3C5.
authors.forename: Jonathan M
authors.initials: JM
authors.lastname: Wilson
authors.affiliation: Neurofarba Department, Università degli Studi di Firenze, 50019 Florence, Italy.
authors.forename: Claudiu T
authors.initials: CT
authors.lastname: Supuran
authors.affiliation: Department of Zoology, University of British Columbia, Vancouver, British Columbia, Canada V6T 1Z4 Faculty of Land and Food Systems, University of British Columbia, Vancouver, British Columbia, Canada V6T 1Z4.
authors.forename: Anthony P
authors.initials: AP
authors.lastname: Farrell
authors.affiliation: Department of Zoology, University of British Columbia, Vancouver, British Columbia, Canada V6T 1Z4.
authors.forename: Colin J
authors.initials: CJ
authors.lastname: Brauner
mesh_terms: D000818:Animals; D002256:Carbonic Anhydrases / Q000378:metabolism*; D005260:Female; D006863:Hydrogen-Ion Concentration; D009206:Myocardium / Q000201:enzymology*; D017684:Oncorhynchus kisutch / Q000378:metabolism*; D010100:Oxygen / Q000097:blood
chemical_list: D002256:Carbonic Anhydrases; D010100:Oxygen
keywords: CA4; Cardiac tissue; Membrane-bound CA; Oncorhynchus; Root effect; Teleost