No Hemoglobin but NO: the icefish(Chionodraco hamatus)heart as a paradigm.

• Main Authors: Pellegrino D., Tota B., PALMERINI, Carlo Alberto
• Other Authors: Pellegrino, D., Palmerini, Carlo Alberto, Tota, B.
• Format: Article in Journal/Newspaper
• Language: English
• Published: 2004
• Subjects: Nitric oxide; icefish; hemoglobin; Antarctic; Antarc*; Icefish
• Online Access: http://hdl.handle.net/11391/164752

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.