No hemoglobin but NO: the icefish (Chionodraco hamatus) heart as a paradigm.
The role of nitric oxide (NO) in cardio-vascular homeostasis is now known to include allosteric redox modulation of cell respiration. An interesting animal for the study of this wide-ranging influence of NO is the cold-adapted Antarctic icefish Chionodraco hamatus, which is characterised by evolutionary loss of hemoglobin and multiple cardio-circulatory and subcellular compensations for efficient oxygen delivery. Using an isolated, perfused working heart preparation of C. hamatus, we show that both endogenous (L-arginine) and exogenous (SIN-1 in presence of SOD) NO-donors as well as the guanylate cyclase (GC) donor 8Br-cGMP elicit positive inotropism, while both nitric oxide synthase (NOS) and sGC inhibitors, i.e. L-NIO and ODQ, respectively, induce significant negative inotropic effects. These results therefore demonstrate that under basal working conditions the icefish heart is under the tonic influence of a NO-cGMP-mediated positive inotropism. We also show that the working heart, which has intracardiac NOS (shown by NADPH-diaphorase activity and immunolocalization), can produce and release NO, as measured by nitrite appearance in the cardiac effluent. These results indicate the presence of a functional NOS system in the icefish heart, possibly serving a paracrine/autocrine regulatory role.
Department of Pharmaco-Biology, University of Calabria, 87030, Arcavacata di Rende, CS, Italy.
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Pellegrino
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Palmerini
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Tota
D000818:Animals; D000864:Antarctic Regions; D001120:Arginine / Q000494:pharmacology; D002316:Cardiotonic Agents / Q000494:pharmacology*; D019069:Cell Respiration / Q000502:physiology; D006152:Cyclic GMP / Q000494:pharmacology; D004563:Electrochemistry; D005455:Fluorescent Antibody Technique; D008981:Molsidomine / Q000031:analogs & derivatives* / Q000494:pharmacology; D009200:Myocardial Contraction / Q000187:drug effects*; D009206:Myocardium / Q000378:metabolism*; D009245:NADH Dehydrogenase / Q000378:metabolism; D009569:Nitric Oxide / Q000378:metabolism*; D019001:Nitric Oxide Synthase / Q000187:drug effects; D009573:Nitrites / Q000378:metabolism; D009792:Oceans and Seas; D009952:Ornithine / Q000031:analogs & derivatives* / Q000494:pharmacology; D010473:Perciformes / Q000378:metabolism*
D002316:Cardiotonic Agents; D009573:Nitrites; D009569:Nitric Oxide; C065027:N(G)-iminoethylornithine; C002385:linsidomine; D001120:Arginine; D008981:Molsidomine; D009952:Ornithine; D019001:Nitric Oxide Synthase; D009245:NADH Dehydrogenase; D006152:Cyclic GMP