EFFECTS OF COLD-ACCLIMATION AND PALMITATE ON ENERGY COUPLING IN DUCKLING SKELETAL-MUSCLE MITOCHONDRIA

Gastrocnemius subsarcolemmal and intermyofibrillar mitochondria were i solated from 5-week-old cold-acclimated and thermoneutral control duck lings, In vitro respiration (polarography) and ATP synthesis (biolumin escence) were determined at 25 degrees C. Subsarcolemmal mitochondria showed a higher state 4 respiration and lower respiratory control and ADP/O ratio in cold-acclimated than in thermoneutral ducklings, Palmit ate decreased the rate of ATP synthesis in both mitochondrial populati ons to about 30% of maximal but failed to abolish this process even at high concentrations, It is suggested that both expensive ATP synthesi s and increased ATP hydrolysis could contribute synergistically to mus cle non-shivering thermogenesis in cold-acclimated ducklings. (C) 1998 Federation of European Biochemical Societies.