MUSCLE BIOENERGETICS IN OBESE ZUCKER RATS

The purpose of this study was to investigate the energetic metabolism in obese Zucker rats, using phosphorus nuclear magnetic resonance spec troscopy at rest and during a 2-Hz muscle stimulation and subsequent r ecovery. Animals were anesthetized with ketamine (150 mg/kg ip). Fed o bese rats and 2-day-fasted obese rats were compared with their normall y fed and 2-day-fasted lean litter mates. No differences were found be tween the two groups for ATP, total creatine, phosphocreatine (PCr), a nd intracellular pH. Starvation in lean rats resulted in a significant fall in inorganic phosphate (Pi), increased resting ADP level, and de creased PCr and ADP recovery after stimulation. The obese rats exhibit ed a decreased PCr/Pi and increased ADP at rest and a decreased PCr re synthesis and ADP metabolization rate after stimulation. Muscle stimul ation in fasted obese rats induced higher PCr depletion and more prono unced acidosis. These results suggest an in vivo mitochondrial metabol ism dysfunction in fasted lean as well as in fed and fasted obese rats .