Carnitine palymityltransferase in neonatal and adult heart and liver mitochondria. Effect of phospholipase C treatment.

Carnitine palmityltransferase was measured in neonatal and adult rat heart and liver mitochondria. When compared to the adult, no developmental differences in liver mitochondrial carnitine palmityltransferase were seen 24 hours postpartum. In neonatal heart, enzyme activity was initially low, reaching adult levels by 20 days. Polarographic measurements of oxygen consumption revealed normal levels of palmityl coenzyme A oxidation in the presence of carnitine and of palmitylcarnitine oxidation in both neonatal heart and liver. Phospholipase C treatment produced higher specific activities of carnitine palmityltransferase in neonatal and activities of carnitine palmityltransferase in neonatal and adult liver, probably due to decreases in total mitochondrial protein. Phospholipase C treatment had no effect on adult rat heart carnitine palmityltransferase but increased neonatal heart enzyme activity to adult levels. Low levels of measured enzyme activity were proposed to be due to "masking" of enzyme expression in intact mitochondrial preparations.