Induction of brain tubulin by triiodothyronine: dual effect of the hormone on the synthesis and turnover of the protein.

The relative effects of triiodothyronine (T3) on the synthesis and turnover of tubulin in the developing rat and chick brain have been examined. Measurements of rates of turnover of radiolabeled tubulin in the hormone-sensitive tissues show that the half-life of tubulin turnover is 4-6 h in the absence of T3 and 10-12 h in the presence of the hormone. Analysis of short-term kinetic data on the stimulation of tubulin by T3 in the chick brain show that the rapid induction is due to a dual effect of the hormone on the metabolism of tubulin--an increase in the rate of synthesis as well as a decline in its rate of turnover.