Ultrastructural study of rat hippocampus after chronic administration of aluminum L-glutamate: an acceleration of the aging process

An ultrastructural study of rat hippocampus was performed on young (group 1 ) and old (group 4) rats receiving daily subcutaneous injections of aluminu m L-glutamate and on old untreated rats (group 5). Young controls were trea ted with sodium L-glutamate (group 2) and physiological saline (group 3). G roup 1 showed vacuolated astrocytes with numerous lipofuscin deposits, mito chondrial swelling, a thinning of the myelin sheath, and many multivesicula r bodies invading the cytoplasm. Cellular structure did not appear to be af fected in groups 2 and 3. Group 4 showed swollen mitochondria, a demyelinat ion process in axonal regions, sizable perivascular oedema with vessel retr action and gliofilament bundles. In this group, lipofuscin deposits in astr ocytes were associated with multivesicular bodies that thinned the myelin s heath to the breaking point; however, no excitotoxic glutamate-induced effe cts were observed. In group 5, extreme cytoplasmic vacuolation was observed , with massive mitochondrial swelling, considerable thinning of the myelin sheath (at times to the breaking point), sizable vacuolar degeneration and gliofilament bundles. These results indicate that ultrastructural alteratio ns in the hippocampus, such as cell vacuolization, massive mitochondrial sw elling and the demyelination process, occur with aging and independently of aluminum intoxication. Similar alterations were observed in aluminum L-glu tamate-intoxicated young rats, but not in controls. These results are consi stent with aluminum-induced acceleration of the aging process. (C) 2001 Els evier Science Inc. All rights reserved.