MEMBRANE ENZYME DEVELOPMENT IN NERVE ENDING MITOCHONDRIA DURING NEONATAL HYPO-THYROIDISM

The effect of propylthiouracil-induced neonatal hypothyroidism on the development of synaptosome fraction mitochondrial membrane enzymes has been determined. Total and specific activities of two mitochondrial inner membrane (cytochrome c oxidase and succinate cytochrome c reductase) and two outer membrane enzymes (monoamine oxidase and rotenone-insensitive NADH cytochrome c reductase) were determined. The inner mitochondrial membrane enzymes developed in synchrony in euthyroid animals, but a decrease in fractional and specific activities of both inner membrane enzymes occurred in hypothyroidism. The outer membrane enzymes developed asynchronously; monoamine oxidase revealed a 9-fold increase while NADH cytochrome c reductase increased 4-fold. Hypothyroidism caused no change in total fractional activity or K(m) and an increased specific activity of outer membrane enzymes.