Stimulation of tubulin synthesis by thyroid hormone in the developing rat brain

The effect of triiodothyronine on the biogenesis of tubulin has been studied in the developing rat brain. In organ cultures of brains from newborn rats, the hormone stimulates the incorporation of [14C]leucine into tubulin by 60-80% within 2 h in the absence of any significant change in total protein synthesis. This stimulation is strictly age-dependent (only brains from late fetal or newborn rats are sensitive), dose-dependent (stimulation increases progressively and reaches a maximum level with physiological dose of the hormone) and displays tissue specificity. The temporal correspondence of the sensitivity of the rat brain to triiodothyronine with the period of normal rise in the level of tubulin and that of the maximal level of nuclear triiodothyronine receptors in the brain strongly suggests the involvement of the hormone in regulating the biogenesis of tubulin during the differentiation and maturation of neonatal rat brain.