Meeting Abstract

P2.132  Friday, Jan. 4  Ultrastructural Adaptations of Skeletal Muscle of young Japanese Quail (Coturnix coturnix japonica) during acclimation CARAGIULO, A.*; OLSON, J.; CZERWINSKI, B.; Villanova University; Villanova University; Villanova University anthony.caragiulo@villanova.edu

Skeletal muscle is the primary site of thermogenesis in birds. Heat generated through contraction during both locomotion and shivering is dependent upon ATP produced primarily by intermyofibrillar mitochondria (IFM). The recent discovery of avian uncoupling protein (avUCP), a homologue of mammalian UCP1, suggests that avian skeletal muscle may also be capable of regulatory non-shivering thermogenesis (NST). If so, avUCP may be localized differentially in subsarcolemmal mitochondria (SSM). Although the role of avUCP in regulatory NST remains unclear, it may play a significant role during development and in conditions that require sustained thermogenesis, such as cold acclimation. We assessed several ultrastructural characteristics of pectoralis (PM) and iliotibialis (IL) muscles in young Japanese Quail during growth and acclimation to determine the ontogenetic changes in mitochondria and whether the IFM and SSM exhibit morphological plasticity during thermal acclimation. Quail were acclimated to cold (5&degC) or warm temperatures (25&degC) for three weeks starting at age 14d. Birds in a third group were dissected at age 14d prior to acclimation. The PM and IL muscles were prepared for electron microscopy and several morphological variables assessed. Preliminary data suggest that several ultrastructural characteristics change ontogenetically and as a result of acclimation, and the PM and IL respond differentially. The area of both IFM and SSM (as %total fiber area) in PM (but not in IL) increased with age and in IFM with acclimation. Cristae become more complex with age and cold acclimation. No evidence exists of a substantial relative increase in SSM with cold-acclimation, suggesting shivering thermogenesis likely remains a primary thermogenic mode.