Horton C, Maden M
Developmental Biology Research Centre, King's College London, United Kingdom.
Dev Dyn. 1995 Mar;202(3):312-23. doi: 10.1002/aja.1002020310.
We have analysed the endogenous retinoids present in whole mouse embryos from day 9 to day 14 of development and in individual components of the embryo at two stages, day 10.5 and day 13, by HPLC. We can only detect two retinoids, all-trans-RA (tRA) and all-trans-retinol (t-retinol), and t-retinol is 5-10-fold in excess over tRA. We cannot detect 9-cis-RA or any didehydroretinoids; thus mammalian embryos seem to differ in their retinoid content from other embryos such as chick, Xenopus, and fish. The levels of tRA do not change significantly over the 6 days of development analysed, whereas t-retinol rises sharply as the liver develops. Within the embryo, tRA is present at high levels in the developing spinal cord and at very low levels in the forebrain; indeed there is a gradient of endogenous tRA from the forebrain to the spinal cord. Other parts of the embryo had intermediate levels of tRA. When a teratogenic dose of RA was administered to day 10.5 embryos, the levels of tRA present in individual tissues of the embryo rose dramatically--from 175-fold to 1,400-fold--and the levels rose in all tissues not in any exclusive areas. We then determined which areas of the embryo were malformed by such a teratogenic dose. The lower jaw, palate, vertebrae, tail, and limbs were consistently abnormal, and since these areas received a dose of tRA no higher than any other it was concluded that cell-specific factors must determine the teratogenic response of these tissues. We then considered whether cellular retinoic acid-binding protein I or II (CRABP I or II) played any role in this response by determining their relative levels in each of the tissues analysed. There was no correlation between the presence of CRABP I and II and the distribution of administered RA. Neither was there a clear correlation in detail between the presence of CRABP I and II and the sites of teratogenesis. We therefore conclude that other factors, for example, nuclear factors, must be responsible for the teratogenic response to RA.
我们通过高效液相色谱法（HPLC）分析了发育第9天至第14天的全小鼠胚胎以及胚胎在第10.5天和第13天这两个阶段的各个组成部分中存在的内源性类视黄醇。我们仅能检测到两种类视黄醇，全反式视黄酸（tRA）和全反式视黄醇（t - 视黄醇），且t - 视黄醇的含量比tRA高出5至10倍。我们无法检测到9 - 顺式视黄酸或任何双脱氢视黄醇；因此，哺乳动物胚胎的类视黄醇含量似乎与其他胚胎（如鸡、非洲爪蟾和鱼类）不同。在所分析的6天发育过程中，tRA的水平没有显著变化，而随着肝脏的发育，t - 视黄醇急剧上升。在胚胎内部，tRA在发育中的脊髓中含量很高，在前脑中含量极低；实际上，从脑前部到脊髓存在内源性tRA的梯度。胚胎的其他部分tRA含量处于中间水平。当给第10.5天的胚胎施用致畸剂量的视黄酸时，胚胎各个组织中tRA的含量急剧上升——从175倍升至1400倍——且所有组织中的含量均上升，并非仅限于某些特定区域。然后我们确定了这种致畸剂量会使胚胎的哪些区域出现畸形。下颌、腭、椎骨、尾巴和四肢始终出现异常，并且由于这些区域接受的tRA剂量并不高于其他区域，因此得出结论，细胞特异性因素必定决定了这些组织的致畸反应。接着我们通过测定所分析的每个组织中细胞视黄酸结合蛋白I或II（CRABP I或II）的相对水平，来考虑它们在这种反应中是否起任何作用。CRABP I和II的存在与施用视黄酸的分布之间没有相关性。CRABP I和II的存在与致畸部位之间也没有详细的明显相关性。因此，我们得出结论，其他因素，例如核因子，必定是对视黄酸致畸反应负责的因素。
