ALPHA-TOCOPHEROL CONCENTRATIONS OF THE NERVOUS-SYSTEM AND SELECTED TISSUES OF ADULT DOGS FED 3 LEVELS OF VITAMIN-E

The effects of dietary vitamin E levels on tissue alpha-tocopherol (al pha-T) concentrations in different parts of the nervous system are lar gely unknown. Therefore, we measured the alpha-T contents of nervous a nd other tissues obtained from beagle dogs fed for two years a vitamin E-deficient diet (-E, 0.05 +/- 0.02 mg vitamin E/kg diet, n = 2), a v itamin E-supplemented diet (+E, 114 +/- 14 mg/kg, n = 2), or a standar d chow diet (E(n), 74 +/- 6 mg/kg, n = 3). Brain regions and spinal co rds of +E dogs contained about double the alpha-T concentrations of E( n) dogs, and about 10-fold those of -E dogs. The various brain regions of -E dogs, compared with E(n) dogs, retained 12-18% of the alpha-T c oncentrations, with the exception of the caudal colliculus, which reta ined 48%. Peripheral nerve alpha-T concentrations in +E dogs (67 ng/mg wet weight) were nearly 5-fold higher than in E(n) dogs (13.4 +/- 5.9 ng/mg) and 80-fold higher than in -E dogs (0.8 ng/mg). Within each di etary group, the lowest alpha-T concentrations in the central nervous system (CNS) were in the spinal cord. Peripheral nerves were the most susceptible to vitamin E repletion or depletion: in +E dogs, nerves co ntained higher concentrations of alpha-T than most brain regions; in E (n) dogs, they contained similar concentrations; but in -E dogs, they contained less alpha-T than most brain regions. Muscles and other tiss ues of -E dogs retained from 1 to 10% of E(n) values. The studies demo nstrate that the CNS conserved alpha-T compared to peripheral nerves a nd nonnervous tissues in adult dogs, but contained lower absolute conc entrations of alpha-T compare with most other tissues.