EFFECTS OF ALTERED OSMOLALITY ON RESPIRATION AND MORPHOLOGY OF MITOCHONDRIA FROM THE DEVELOPING BRAIN

Abstract— The effects of altered osmolality on respiration and fine structure were studied in isolated cerebral mitochondria from mature rats (60‐100 days of age) and from rat pups in the first month of postnatal life (5, 10, 20 and 30 days). In the mature cerebral mitochondria, ADP‐dependent respiration was inhibited in media of decreased osmolality. There was a transient inhibition of ADP‐dependent respiration and a sustained increase in ADP‐independent respiration in media of increased osmolality. In contrast, cerebral mitochondria from 5‐day‐old rats showed both inhibition of ADP‐dependent respiration and increased ADP‐independent respiration in hypo‐osmolal media. In these mitochondria, inhibition of ADP‐dependent respiration was stable and ADP‐independent respiration was unchanged in media of increased osmolality. The transition to the mature respiratory response occurring with altered osmolality took place between 10 and 30 days of age. During this same age period, cerebral mitochondria showed an increasing resistance to matrix condensation in media of normal and increased osmolality. Copyright © 1979, Wiley Blackwell. All rights reserved