Beckman D A, Tu C
Department of Pediatrics, Thomas Jefferson University, Philadelphia, Pennsylvania, USA.
Reprod Toxicol. 1997 Nov-Dec;11(6):875-7. doi: 10.1016/s0890-6238(97)00071-3.
Protein has been shown to be the principal source of leucine for the Day 8.5 to 10.5 rat conceptus in culture. It could be argued that this finding applies only after adaptation to culture conditions and does not apply in vivo. This possibility was investigated using an isotope-dilution technique after i.v. injection of [3H]leucine into Day 10.5 pregnant rats. Specific radioactivity of free leucine in the conceptus was 8 to 10% of that in maternal plasma. Slow exchange of leucine with the maternal circulation and fetal tissue protein turnover were judged to be inadequate as explanations for the observed isotope dilution. Taken together, our results and those from in vitro studies are consistent with a major contribution of leucine coming from the degradation of protein in vivo, probably involving the visceral yolk sac. Our results suggest that mechanisms of amino acid supply to the conceptus identified using whole-embryo culture mirror those in vivo.
已表明蛋白质是体外培养的第8.5至10.5天大鼠胚胎亮氨酸的主要来源。可以认为这一发现仅适用于适应培养条件后，并不适用于体内情况。利用同位素稀释技术对第10.5天的怀孕大鼠静脉注射[3H]亮氨酸后，对这种可能性进行了研究。胚胎中游离亮氨酸的比放射性为母体血浆中的8%至10%。亮氨酸与母体循环的缓慢交换以及胎儿组织蛋白质周转被认为不足以解释观察到的同位素稀释现象。综合来看，我们的结果以及体外研究的结果一致表明，亮氨酸的主要来源是体内蛋白质的降解，可能涉及内脏卵黄囊。我们的结果表明，利用全胚胎培养确定的胚胎氨基酸供应机制与体内机制相同。
