The Regional and Intracellular Distribution of Arylsul- Fatase and Evidence F O R Two Populations of Lysosomes in Rat Brain

Following the original observation of Beaufay et al. 3, the presence of lysosomes in brain has been amply documented and a lysosomal localization for the following acid hydrolases establishedlS,18,Zl,27,28: acid phosphatase (EC 3.1.3.2), fl-2-acetylamino-2-deoxy-D-glucohydrolase (N-acetylglucosaminidase) (EC 3.2.1.30), fl-galactosidase (EC 3.2.l.23), fl-glucuronidase (EC 3.2.1.31), acid ribonuclease (EC 2.7.7.16), acid deoxyribonuclease and cathepsin. Less is known, however, about the intracellular localization of several other hydrolases, also detected in nervous tissue, e.g. arylsulfatase (EC 3.1.6.1) (refs. 2, 8), neuraminidase (EC 3.2.1.18) (ref. 22), and flglucosidase (EC 3.2.1.21) (ref. 10). Regionally, the lysosome has been seen in the electron microscope, inter alia, in peripheral nerve la, the pineal gland 1, the cerebellum 11 and the cerebral cortex ts, while histochemicallt, t9 and ultramicrochemical2a, zl techniques have suggested its presence in several other brain regions and brain tumors t2, as well. Functionally 7, iysosomes have been implicated in the response of the nervous tissue to various injurious agents or treatments such as nerve crush 13, nerve transection 17, convulsants 29 and viral infection 15. A specialized role for lysosomes in the neonatal period has also been suggested 4. The present study approaches the possibility of qualitative differences among lysosomes of rat brain cortex, hypothalamus and thalamus. Secondly, it reports on the activity of two lysosomal hydrolases, arylsulfatase (sulfatase) and N-acetylglucosaminidase (NPG-ase), in a total of 6 rat brain regions, the premise for this aspect of the study being that the existence of interregional differences in enzyme activity and/or properties may reflect a microheterogeneity of lysosomes which in turn may aid in the biochemical characterization of a given brain structure known to be endowed with specific functions. A preliminary report has appeared so.