title: Dynamic changes in cardiac mitochondrial metabolism during warm acclimation in rainbow trout.
abstract: Although the mitochondrial metabolism responses to warm acclimation have been widely studied in fish, the time course of this process is less understood. Here, we characterized the changes of rainbow trout (Oncorhynchus mykiss) cardiac mitochondrial metabolism during acute warming from 10 to 16°C, and during the subsequent warm acclimation for 39 days. We repeatedly measured mitochondrial oxygen consumption in cardiac permeabilized fibers and the functional integrity of mitochondria (i.e. mitochondrial coupling and cytochromeceffect) at two assay temperatures (10 and 16°C), as well as the activities of citrate synthase (CS) and lactate dehydrogenase (LDH) at room temperature. LDH and CS activities significantly increased between day 0 (10°C acclimated fish) and day 1 (acute warming to 16°C) while mitochondrial oxygen consumption measured at respectivein vivotemperatures did not change. Enzymatic activities and mitochondrial oxygen consumption rates significantly decreased by day 2, and remained stable during warm acclimation (days 2-39). The decrease in rates of oxygen between day 0 and day 1 coincided with an increased cytochromeceffect and a decreased mitochondrial coupling, suggesting a structural/functional impairment of mitochondria during acute warming. We suggest that after 2 days of warm acclimation, a new homeostasis is reached, which may involve the removal of dysfunctional mitochondria. Interestingly, from day 2 onwards, there was a lack of differences in mitochondrial oxygen consumption rates between the assay temperatures, suggesting that warm acclimation reduces the acute thermal sensitivity of mitochondria. This study provides significant knowledge on the thermal sensitivity of cardiac mitochondria that is essential to delineate the contribution of cellular processes to warm acclimation.
authors.affiliation: Department of Chemistry and Biochemistry, University of Moncton, Moncton, New Brunswick, Canada E1A 3E9 nicolas.pichaud@umoncton.ca.|Department of Biological and Environmental Sciences, University of Gothenburg, SE-405 30 Gothenburg, Sweden.
authors.forename: Nicolas
authors.identifier: 0000-0002-2820-8124
authors.initials: N
authors.lastname: Pichaud
authors.affiliation: Department of Biological and Environmental Sciences, University of Gothenburg, SE-405 30 Gothenburg, Sweden.
authors.forename: Andreas
authors.initials: A
authors.lastname: Ekström
authors.affiliation: Department of Biological and Environmental Sciences, University of Gothenburg, SE-405 30 Gothenburg, Sweden.
authors.forename: Kim
authors.initials: K
authors.lastname: Hellgren
authors.affiliation: Department of Biological and Environmental Sciences, University of Gothenburg, SE-405 30 Gothenburg, Sweden.
authors.forename: Erik
authors.initials: E
authors.lastname: Sandblom
mesh_terms: D000064:Acclimatization; D000818:Animals; D002950:Citrate (si)-Synthase / Q000378:metabolism; D007770:L-Lactate Dehydrogenase / Q000378:metabolism; D008929:Mitochondria, Heart / Q000378:metabolism*; D009206:Myocardium / Q000378:metabolism; D017686:Oncorhynchus mykiss / Q000378:metabolism*; D010101:Oxygen Consumption; D013696:Temperature
chemical_list: D007770:L-Lactate Dehydrogenase; D002950:Citrate (si)-Synthase
keywords: Electron transport system; Fish; Heart; Mitochondria; Temperature; Warm acclimation