Activity of sorbitol dehydrogenase during development of the rat brain

The postnatal development of the sorbitol dehydrogenase (SDH) activity in rat brain was investigated in different ontogenetic stages by a photometric assay. The specific activity increases from birth up to 45 days of age and then decreases again. The developmental pattern is similar in all brain regions investigated but differs in the peak activity: Brain regions containing large proportions of white matter, e.g. pons, develop activities of SDH which are up to two times higher than those in regions consisting predominantly of gray matter, e.g. cerebral cortex. These results suggest that SDH may be localized predominantly in astrocytes typical for white matter (i.e. fibrous astrocytes) and/or in oligodendrocytes but is not necessarily restricted to a specialized type of astrocyte. From the results it is concluded that the activity of SDH is regulated metabolically.