Cytochrome reductase activities in rat brain microsomes during development.

Postnatal developmental alterations of microsomal NADH-cytochrome b5 reductase and NADPH-cytochrome c reductase activities were determined in the brain of rats. The reductase activities increased from a low level in the immature brain to a maximum level at 23 to 30 days of age, and then decreased slightly to a plateau. The periods of the activity increments were in accord with those of the enhancement of microsomal fatty acid elongation. The specific activities of these reductases were high in cerebral hemispheres and medulla oblongata, intermediate in midbrain, and lowest in cerebellum of the four regions of 20-day-old rat brain.