Meeting Abstract

P2.70  Friday, Jan. 4  Adaptive response of Japanese Quail (Coturnix coturnix japonica) to cold acclimation: physiological changes and localization of avUCP in skeletal muscle CZERWINSKI, B.*; OLSON, J.; CARAGIULO, A.; Villanova University; Villanova University; Villanova University brenda.czerwinski@villanova.edu

The discovery of a nuclear-encoded, mitochondrial transmembrane avian uncoupling protein has challenged the primacy of shivering thermogenesis in birds. Avian UCP (avUCP) is a homologue of mammalian UCP1 which uncouples oxidative phosphorylation from ATP synthesis to promote high metabolic rates and heat production in brown adipose tissue. If functionally similar to UCP1, avUCP may be upregulated after cold exposure to play a central role in nonshivering thermogenesis. However, previous work shows that avUCP is expressed predominantly in skeletal muscle; low ATP production would be counterproductive to the large demand for ATP during contraction. To prevent the debilitating effects of low ATP production during shivering, avUCP may be differentially expressed in subsarcolemmal mitochondria (SSM) relative to intermyofibrillar mitochondria (IFM). Alternatively, avUCP may play a supportive role during periods of high catabolic flux (as during prolonged cold exposure) by loosely uncoupling mitochondria to prevent redox imbalances and/or protect against oxidative mitochondrial damage. To examine these possibilities, we acclimated 2-5 wk old Japanese Quail to warm (25 &degC) or cold (5 &degC) and (1) detected the presence of avUCP mRNA with RT/PCR using gene-specific primers for chicken avUCP and (2) assayed the presence of avUCP protein in SSM and IFM isolates from pectoralis muscles using immunoblots with antibodies to mammalian UCP3. Avian UCP mRNA was present in all birds, the first demonstration in quail. Avian UCP protein was present only in IFM of both acclimation groups, with apparently more after cold. Localization of avUCP to IFM in pectoralis suggests a function in mitochondrial protection or redox maintenance during catabolism.