Human cytochrome c oxidase during cardiac growth and development.

Human heart mitochondrial cytochrome c oxidase specific content and specific activity was measured in five fetuses 15-21 weeks gestational age and in five patients whose age ranged from 6 days to 22 years. None had evidence of cardiac pathology. An increase in cytochrome c oxidase specific content and specific activity was observed in the fetal heart with increasing gestational age (0.13-0.38 nmol heme a/mg protein and 67-295 nmol O2 utilized/min/mg protein) and from the neonatal period (0.35 nmol heme a/mg protein and 140 nmol O2/min/mg protein) to adulthood (1.2 nmol heme a/mg protein and 1104 nmol O2/min/mg protein). A marked increase was observed postnatally between 4 and 19 months.