A COMPARATIVE STUDY OF BRAIN AND LIVER MITOCHONDRIA FROM NEW-BORN AND ADULT RATS

A method has been developed for the estimation of organelle number in subcellular fractions and applied to the estimation of the mitochondrial content of brain and liver from new‐born and adult rats. The respiratory enzyme content per mitochondrion of the adult brain was 3·5 times greater than that of the neonate. This increase in enzyme content was not correlated with an increase in the mean size of the organelle. The succinate dehydrogenase activity per mitochondrion of the livers from neonatal and adult rats showed no obvious change. There was, however, an increase in the mean size of the organelle. These findings are discussed with reference to the development of the brain and to the development of mitochondria. Copyright © 1969, Wiley Blackwell. All rights reserved