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First published online July 14, 2008
Journal of Experimental Biology 211, 2460-2466 (2008)
Published by The Company of Biologists 2008
doi: 10.1242/jeb.018143

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In vivo regulation of rainbow trout lipolysis by catecholamines

Leonardo Magnoni^*, Eric Vaillancourt and Jean-Michel Weber

Biology Department, University of Ottawa, 30 Marie Curie, Ottawa, Ontario, Canada, K1N 6N5

View larger version (15K): [in this window] [in a new window]   Fig. 1. Control experiments showing the effect of vehicle saline infusion (shaded area, filled circles) on (A) glycerol concentration in plasma, (B) specific activity (SA) and (C) rate of appearance (Ra glycerol) in resting trout. Measurements were made by continuous infusion of [3H]glycerol. No significant differences were found (P>0.05). Values are means ± s.e.m. (N=4).

View larger version (14K): [in this window] [in a new window]   Fig. 2. Effects of exogenous norepinephrine (NE) infusion (shaded area, filled circles) on (A) glycerol concentration in plasma, (B) specific activity (SA) and (C) rate of appearance (Ra glycerol) in resting trout. Asterisks indicate significant differences (P<0.001) from baseline values determined at 90 min. Values are means ± s.e.m. (N=8).

View larger version (16K): [in this window] [in a new window]   Fig. 3. Effects of exogenous epinephrine (Epi) infusion (shaded area, filled circles) on (A) glycerol concentration in plasma, (B) specific activity (SA) and (C) rate of appearance (Ra glycerol) in resting trout. Asterisks indicate significant differences (P<0.001) from baseline values determined at 90 min. Values are means ± s.e.m. (N=8).

View larger version (7K): [in this window] [in a new window]   Fig. 4. Relationship between glycerol turnover (Ra glycerol) and glycerol concentration in resting trout during administration of saline (stars), norepinephrine (unfilled circles) or epinephrine (filled circles). Only values measured during the final 10 min of administration of saline, epinephrine and norepinephrine are included (110–120 min in Figs 1, 2, 3). Lines were fitted by linear regression for saline (y=4.326–0.375x), continuous line, r2=0.03, slope not different from 0 (P=0.905); for norepinephrine (y=2.750+0.860x), broken line, r2=0.05, slope not different from 0 (P=0.830); and for epinephrine (y=4.286+5.944x), dotted line, r2=0.48, slope different from 0 (P<0.05). Values are means ± s.e.m. (N=4 for saline and N=8 for catecholamines).

View larger version (5K): [in this window] [in a new window]   Fig. 5. Ratio of lipolytic rate (Ra glycerol) over metabolic rate (O2) for vertebrates measured to date. Values correspond to vertebrates at rest and during exercise at equivalent intensities (40–70% O2,max), except for birds, where only data for shivering are available (Vaillancourt and Weber, 2007). Ratios were calculated from the following studies: rat (McClelland et al., 2001), goat (Weber et al., 1993), dog (Issekutz et al., 1967; Issekutz et al., 1975), human (Wolfe et al., 1990), ruff sandpiper (Vaillancourt and Weber, 2007) and trout [present study and Bernard et al. (Bernard et al., 1999) using O2 values from Burgetz et al. (Burgetz et al., 1998)]. The broken line shows the calculated average ratio for resting and exercising endotherms (0.016).

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