IMMUNOCYTOCHEMICAL LOCALIZATION OF CATALASE IN THE CENTRAL-NERVOUS-SYSTEM OF THE RAT

Catalase is a marker for peroxisomes, which are ubiquitous cytoplasmic organelles. Although the distribution and features of peroxisomes are well known in liver and kidney, these organelles have been rarely stu died in neural tissues. Catalase is an important scavenging enzyme aga inst reactive oxygen species, as it removes H2O2 produced during metab olic processes. Reactive oxygen species are involved in a number of br ain lesions and in brain aging, We investigated the distribution of ca talase in rat central nervous system by means of a newly developed imm unocytochemical procedure for signal enhancement, using an affinity-pu rified polyclonal antiserum. The data show that catalase immunoreactiv ity is present in all neural cells, both neuronal and glial, albeit at different concentrations. Among glial cells, ependymal cells and tany cytes of the third ventricle and the median eminence show the most int ense immunoreaction; positivity is also found in oligodendrocytes and astrocytes. In general, neurons in the brainstem are relatively more i mmunoreactive than those in the forebrain although, within these respe ctive brain regions, there ate areas with low and high staining intens ity. Moreover, within the same area, certain types of neuron appear mo re immunoreactive than others. The cell bodies in the septal nuclei, p allidum, reticular thalamic nucleus, mesencephalic nucleus of the trig eminal nerve, Deiter's nucleus, locus ceruleus, cranial and spinal mot or nuclei, and the Golgi cells of the cerebellar cortex are among the most densely stained neurons. Catalase immunoreactivity of the cell bo dies, which presumably is proportional to catalase content, appears to be only partially correlated with cell size or type of neurotransmitt er used in the nerve endings; it is likely that other unknown paramete rs regulate the abundance of the enzyme. In many cases, highly immunor eactive cells correspond to neurons known to be resistant to ischemia- reperfusion injury, whereas weakly stained cells correspond to neurons that are more susceptible to ischemic damage. The amount of catalase may be critical for a protective effect against oxidative stress under pathological conditions, such as ischemia-reperfusion injury.