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First published online May 24, 2004
Journal of Experimental Biology 207, 2305-2311 (2004)
Published by The Company of Biologists 2004
doi: 10.1242/jeb.01017

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Respiration rate of hepatocytes varies with body mass in birds

Paul L. Else^1,*, M. D. Brand³, N. Turner¹ and A. J. Hulbert²

¹ Department of Biomedical Science, Metabolic Research Centre, University of Wollongong, Wollongong, NSW 2522, Australia
² Department of Biological Science, Metabolic Research Centre, University of Wollongong, Wollongong, NSW 2522, Australia
³ MRC-Dunn Human Nutrition Unit, Hills Road, Cambridge CB2 2XY, UK

View larger version (18K): [in a new window]   Fig. 1. The allometric relationship between body mass Mb (kg) and basal metabolic rate (BMR) for the bird species used in the current study. See Table 1 for names of individual species.

View larger version (18K): [in a new window]   Fig. 2. The allometric relationship between liver mass (g) and body mass Mb (kg) of different-sized birds. Values are means ± S.E.M.; N=4 for all bird species.

View larger version (16K): [in a new window]   Fig. 3. The allometric relationship between respiration rate of isolated hepatocytes (HRR) and body mass Mb (kg) of different-sized birds. (A) HRR expressed per mg dry mass; (B) HRR expressed per mg protein. Values are means ± S.E.M. N=4 for all bird species except sparrows in A (N=2).

View larger version (19K): [in a new window]   Fig. 4. The relationship between the calculated cellular protein content (ng) of hepatocytes and body mass (kg) of different-sized birds. Values are means ± S.E.M. N=4 for all bird species except finches and pigeons (N=3).

View larger version (29K): [in a new window]   Fig. 5. The allometric relationship between the amount of the respiration rate of hepatocytes (HRR) devoted to four subcellular activities and body mass of different-sized birds. The subcellular activities are: mitochondrial ATP production (A), mitochondrial proton leak (B), non-mitochondrial oxygen consumption (C), and the activity of the Na+ pump (D). Values are means ± S.E.M. N=4 for all bird species except for geese (N=3) and sparrows (N=2), and (in B only) starlings (N=3) and finches (N=2).

View larger version (19K): [in a new window]   Fig. 6. The allometric relationship between calculated resting respiration rate of the whole liver (LRR) in different-sized birds and body mass. Values are means ± S.E.M. N=4 for all bird species except sparrows (N=2).

View larger version (19K): [in a new window]   Fig. 7. A comparison of hepatocyte respiration in birds and mammals. (A) An allometric plot of the hepatocyte respiration rates (HRR) for different-sized birds (broken line) compared to the relationships (solid lines) previously described for mammals (from Porter and Brand, 1995) and ectotherms (from Hulbert et al., 2002a). (B) The composition of hepatocyte respiration for two birds (zebra finch and emu) and two mammals (mouse and horse). (Bi) The absolute values (in nmol O2 mg–1 dry mass min–1) for these four species; (Bii) the relative composition for the same species.