Measurement of local rates of brain protein synthesis by quantitative autoradiography: validation with L-[3H]valine.

Following the injection of 4-day old rats with 150 mM L-[3,4-3H]valine (10 mumol/g, IP) the incorporation of 3H into protein was linear 2 hours. Valine specific activity in the brain acid-soluble fraction was constant between 30 and 120 min after injection with a mean value of 82.3% of the injectate. Significant amounts of tritated metabolites accumulated in the brain acid-soluble fraction (41.4% of radioactivity at 120 min) but do not prove an impediment to measuring rates of protein synthesis. The rate of protein synthesis in cerebral cortex of the 4-day old rat was measured by quantitative autoradiography using [3H]valine and 3H-sensitive film. The measured rate shows excellent agreement with that found previously using L-[1-14C]valine. Our results suggest that [3H]valine can be a useful precursor to measure local rates of brain protein synthesis by quantitative autoradiography.