Localization of Hexokinase in Neural Tissue: Electron Microscopic Studies of Rat Cerebellar Cortex

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Abstract
The distribution of hexokinase (ATP:D-hexose 6-phosphotransferase, EC 2.7.1.1) in rat cerebellar cortex was studied at the EM level using the peroxidase-antiperoxidase procedure. Extensive staining of cytoplasmic regions, with some increased staining at mitochondrial profiles, was seen in the cell bodies of neurons (basket, stellate, Lugaro, Golgi and granule cells) and astrocytes. Oligodendrocytes showed little or no detectable staining. Purkinje cell perikarya were much less intensely stained than were the perikarya of other neurons. The initial portion of the Purkinje dendrite was, like the perikaryon from which it emerged, lightly stained. More intense stained was seen in the secondary and tertiary branches of the Purkinje dendrite; the terminal branches were devoid of stain. Granule cell dendrites were well stained in their initial portions but devoid of stain in their terminal dendritic digits which form part of the cerebellar glomeruli. In contrast to the unstained granule cell dendritic digits, the central mossy fiber nerve terminal of the glomerulus exhibited intense staining of the mitochondrial profiles and of synaptic vesicles adjacent to the mitochondria. Basket cell axons showed intense staining in the segments adjacent to the Purkinje cell soma; terminal twigs of the basket axons in the pinceau surrounding the (unstained) initial segment of the Purkinje axon showed markedly decreased staining intensity. There may be substantial variation in hexokinase levels between the various regions of neuronal processes. Hexokinase was seen at cytoplasmic and mitochondrial locations in a variety of cells. Location of hexokinase can not probably be directly correlated with cell type, i.e., with neurons versus glia. Relative levels of hexokinase may be indicative of relative glycolytic capacity.