Biochemical and functional evidences for a GLUT-4 homologous protein in avian skeletal muscle.

The characteristics and modulation of glucose transport were investigated in skeletal muscles of 5-wk-old Muscovy ducklings (Cairina moschata). Glucose uptake by sarcolemmal vesicles isolated from gastrocnemius muscle followed typical Michaelis-Menten kinetics with a K(m) value (17 mM) similar to that described in equivalent mammalian preparations. Western blot analysis of duckling sarcolemma using antibodies directed against rat GLUT-4 transporter revealed an immunoreactive protein of similar molecular mass (45 kDa) to that present in rats.

Hormonal control of thermogenesis in perfused muscle of Muscovy ducklings.

Endocrine stimulation of muscle nonshivering thermogenesis (NST) in ducklings was investigated in vitro using a perfused hindlimb preparation maintained at 25 degrees C. Effects of flow rate, norepinephrine (NE), epinephrine, and glucagon on perfused muscle oxygen consumption (MO2) and perfusion pressure were studied. Control ducklings (Cairina moschata, 5 wk old) reared at thermoneutrality (25 degrees C, TN) were compared with two age-matched groups exhibiting muscle NST in vivo: cold-acclimated ducklings (4 degrees C, 4 wk, CA) and glucagon-treated ducklings (103 nmol/kg twice-daily, intraperitoneally, GT).