Alteration of the alpha-tocopherol content in the brain and peripheral nervous tissue of dysmyelinating mutants

Alteration of delta-6 desaturase by vitamin E in rat brain and liver

delta-6 Desaturase, measured at substrate saturation using linoleic acid, was found to be increased by more than two-fold when the content of vitamin E in brain microsomal membrane suspension was increased (up to 7.5 micrograms/mg membrane protein, i.e. 100 micrograms/g tissue from which microsomes were prepared). In contrast, this activity was reduced by 25% in the liver. This raises the question of the multiple role of vitamin E in membranes, the control of membrane polyunsaturated fatty acids through synthesis, and their protection against peroxidation.

Alteration of alpha-tocopherol content in the developing and aging peripheral nervous system: persistence of high correlations with total and specific (n-6) polyunsaturated fatty acids

In contrast to brain, the sciatic nerve concentration of vitamin E in rats increased rapidly during the postnatal period (approximately fivefold between days 1 and 8), then decreased dramatically (about twofold between days 8 and 30), and further decreased slowly between days 30 and 60 and remained constant up to 2 years. Although the sciatic nerve concentration of vitamin E decreased by 58% between days 8 and 30, the concentration of vitamin E in serum presented a marked decrease (approximately 75%). The vitamin E concentrations varied in a similar pattern in whole sciatic nerve and in endoneurium and showed a very close correlation (r = 0.94). The age-related changes in fatty acid concentration of the endoneurial fraction of the sciatic nerve were characterized by a large increase in content of saturated and monounsaturated fatty acids up to 6 months (twofold for saturated and fourfold for monounsaturated fatty acids). Then, up to 24 months, the amount of these fatty acids decreased very slowly. The content of (n-6) polyunsaturated fatty acids (PUFAs) decreased rapidly up to 1 year and slowly afterward. In contrast, during development the amount of (n-3) PUFA was relatively stable and decreased during aging. A highly significant correlation between vitamin E and (n-6) PUFA [18:2(n-6), 20:4(n-6), and total (n-6)] was observed but not between (n-3) PUFA and vitamin E. It is suggested that there may be a relationship between vitamin E and (n-6) PUFA in the PNS membranes during development and aging.