Differences in proton leak kinetics, but not in UCP3 protein content, in subsarcolemmal and intermyofibrillar skeletal muscle mitochondria from fed and fasted rats

We have investigated the effect of 24-h fasting on basal proton leak and un coupling protein (UCP) 3 expression at the protein level in subsarcolemmal and intermyofibrillar skeletal muscle mitochondria. In fed rats, the two mi tochondrial populations displayed different proton leak, but the same prote in content of UCP3. In addition, 24-h fasting, both at 24 and 29 degreesC, induced an increase in proton leak only in subsarcolemmal mitochondria, whi le UCP3 content increased in both the populations. From the present data, i t appears that UCP3 does not control the basal proton leak of skeletal musc le mitochondria. (C) 2001 Federation of European Biochemical Societies. Pub lished by Elsevier Science B.V. All rights reserved.