Thermal sensitivity of mitochondrial function in the Antarctic Notothenioid Lepidonotothen nudifrons |
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Authors: | I Hardewig H O Pörtner L S Peck |
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Institution: | (1) Alfred Wegener Institute for Polar and Marine Research, Biology I/Ecophysiology, Columbusstrasse, D-27568 Bremerhaven, Germany, DE;(2) British Antarctic Survey, Cambridge CB3 OET, UK, GB;(3) Institute of Freshwater Ecology and Inland Fisheries, Department of Biology and Ecology of Fishes, Müggelseedamm 310, D-12587 Berlin, Germany e-mail: hardewig@igb-berlin.de Tel.: +49-030-64181614; Fax: +49-030-64181750, DE |
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Abstract: | The thermal sensitivity of mitochondrial function was investigated in the stenothermal Antarctic fish Lepidonotothen nudifrons. State 3 respiration increases with increasing temperature between 0 °C and 18 °C with a Q
10 of 2.43–2.63. State 4 respiration in the presence of oligomycin, an inhibitor of mitochondrial ATP synthase, quantifies the
leakage of protons through the inner mitochondrial membrane, which causes oxygen consumption without concomitant ATP production.
This parameter shows an unusually high Q
10 of 4.21 ± 0.42 (0–18 °C), which indicates that proton leakage does not depend merely on ion diffusion but is an enzyme-catalysed
process. The differential thermal sensitivity of oxidative phosphorylation (=state 3) and proton leakage (=state 4 in the
presence of oligomycin) leads to progressive uncoupling of the mitochondria and decreased efficiency of oxidative phosphorylation
under in vivo conditions if the body temperature of L. nudifrons increases.
Accepted: 2 September 1999 |
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Keywords: | Antarctic fish Temperature Mitochondrial respiration Proton leakage Isocitrate dehydrogenase |
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