Axonal caliber and neurofilaments are proportionately decreased in galactose neuropathy

Feeding galactose to rats induces nerve conduction abnormalities, increased levels of nerve galactitol, endoneurial edema, elevated pressure and hypoxia of endoneurial fluid, and pathological abnormalities of nerve fibers. To investigate the cellular mechanisms of the fiber lesions and their possible relationship to alterations in the nerve microenvironment, rat peroneal nerves were morphometrically evaluated eight months after the commencement of galactose feeding. Whereas the density of neurofilaments (NF/μm²) in the transverse axonal area of myelinated fibers was not significantly different between the nerves of galactose-fed and control rats, axonal areas and the number of NF/axon, when related to myelin spiral length, were significantly less in nerves of galactose-fed rats. Myelin alterations, characteristic of axonal atrophy, were also significantly increased. The present data provide evidence of a proportionate decrease in axonal caliber and the number of NF/axon in myelinated fibers in experimental galactose neuropathy, suggesting that galactose induces either decreased NF synthesis, assembly or transport. The possible role of microenvironmental alterations, including endoneurial hypoxia and hyperosmolarity, in the production of this axonal atrophy is discussed.