Incorporation of (14C) leucine into protein and tubulin by brain slices from young and old mice.

Tubulin, the protein of neurotubules, aids in the movement of other proteins and organelles within axons and may be involved in the pathogenesis of senile dementia in man. This led us to investigate the effect of age on the synthesis of tubulin and of total brain protein of mice. Brain slices from 5-, 12-, 18-, and 25 mo.-old mice were incubated with [14C] leucine. The slices were then homogenized and tubulin was precipitated from the 100,000g supernate by vinblastine. Protein synthesis was measured by [14C] leucine incorporation into hot trichloroacetic acid-insoluble protein and tubulin was quantitated by [3H] colchicine binding. The 4 age groups did not differ significantly in the relative specific activities of their total protein or of their tubulin. The content of the colchicine-binding protein (tubulin) also was not affected by age. These findings suggest that, at least in mice, aging does not significantly affect the rate of synthesis of brain protein or tubulin.