Effect of retinoid status on alpha, beta and gamma retinoic acid receptor mRNA levels in various rat tissues.
Effect of retinoid status on alpha, beta and gamma retinoic acid receptor mRNA levels in various rat tissues.
复制标题
类维生素A状态对各种大鼠组织中α、β和γ视黄酸受体mRNA水平的影响。
作者：
S. Kato;H. Mano;T. Kumazawa;Y. Yoshizawa;R. Kojima;S. Masushige
我们研究了类维生素a、维生素D和甲状腺激素对完整动物视黄酸受体(RAR) α、RAR β和RAR γ mrna水平的影响。虽然维生素A缺乏没有引起RAR α和RAR γ mrna水平的显著变化，但维生素A缺乏大鼠各组织中RAR β转录本水平大幅下降，但在给予维甲酸后迅速恢复到正常水平。视黄醇也能恢复RAR β mRNA水平，但诱导的幅度和动力学与视黄酸不同。特异性抑制剂的使用表明，体内RAR β基因表达的自动调节发生在转录水平。此外，从这些结果可以推测，维持正常的RAR β mRNA水平似乎需要一个阈值血清视黄醇浓度（约25微克/分升）。此外，我们发现，与RAR β mRNA的对照水平相比，正常大鼠给予视黄醇和视黄酸导致RAR β转录物的过度表达（2-15倍），尽管RAR α和RAR γ mRNA的水平没有受到影响。维生素D和甲状腺激素不能调节RAR转录本的水平。这些发现清楚地表明，在完整的动物中，RAR β基因表达的特异性配体调控。根据类视黄醛状态改变的RAR β水平可能影响类视黄醛诱导的基因表达。
We have investigated the effects of retinoids, vitamin D and thyroid hormone on the levels of retinoic acid receptor (RAR)alpha, RAR beta and RAR gamma mRNAs in intact animals. Although vitamin A deficiency caused no significant changes in the levels of RAR alpha and RAR gamma mRNAs, the level of RAR beta transcripts was greatly decreased in various tissues of vitamin A-deficient rats, but was restored rapidly to a normal level after administration of retinoic acid. Retinol also restored the RAR beta mRNA level, but the magnitude and kinetics of the induction differed from those by retinoic acid. The use of specific inhibitors demonstrated that this autoregulation of RAR beta gene expression in vivo occurred at the transcriptional level. In addition, from these results it was postulated that the maintenance of the normal RAR beta mRNA levels seemed to require a threshold serum retinol concentration (about 25 micrograms/dl). Moreover, we found that administration of retinol and retinoic acid to normal rats caused the overexpression of RAR beta transcripts (2-15-fold) when compared with the control levels of RAR beta mRNA, although the levels of RAR alpha and RAR gamma mRNAs were not affected. Vitamin D and thyroid hormone did not modulate the levels of RAR transcripts. These findings clearly indicate the specific ligand regulation of RAR beta gene expression in intact animals. The altered levels of RAR beta according to retinoid status may affect retinoid-inducible gene expression.