Allometry of mitochondrial proton leak: influence of membrane
surface area and fatty acid composition.
Porter, Richard K., A. J. Hulbert & Martin D. Brand.
Department of Biochemistry, University of Cambridge, Tennis Court
Road, Cambridge CB2 1QW, UK, Department of Biochemistry, Trinity
College Dublin, Dublin 2, Ireland and Department of Biological
Sciences, University of Wollongong, Wollongong, New South Wales 2522,
Australia
APStracts 3:0200R, 1996.
We investigated why liver mitochondria from small mammals are leakier
to protons than those from larger mammals. 69% + 23% of the proton
leak differences appeared to relate to membrane area (less inner
membrane surface area in larger animals); any residual differences
must reflect differences in membrane properties. There were
differences in phospholipid fatty acid composition: unsaturation
index, monounsaturates, palmitate (16:0), stearate (18:0),
docosahexaenoate (22:6n3) and the 22:6n3/22:5n3 ratio all correlated
with body mass. Proton flux per cm2 did not correlate significantly
with body mass or, in general, with phospholipid fatty acid
composition, suggesting little role for fatty acid composition in
determining proton leak in mammals of different body mass. However,
unsaturation index and n3 polyunsaturated fatty acid content
correlated significantly with proton leak per mg phospholipid when
literature data from reptiles and rats in different thyroid states
was included, giving some support to suggestions of a general role
for phospholipid fatty acid composition in determining mitochondrial
proton leak.
Received 26 January 1996; accepted in final form 14 May 1996.
APS Manuscript Number R52-6.
Article publication pending Am. J. Physiol. (Regulatory Integrative
Comp. Physiology).
ISSN 1080-4757 Copyright 1996 The American Physiological Society.
Published in APStracts on 5 June 96