Speake Brian K, Herbert Jacquie F, Thompson Michael B
Animal Health Group, SAC, West Mains Road, Edinburgh, EH9 3JG, UK.
Comp Biochem Physiol A Mol Integr Physiol. 2004 Oct;139(2):213-20. doi: 10.1016/j.cbpb.2004.09.004.
During gestation in the viviparous lizard Pseudemoia entrecasteauxii, the fetus obtains nutrients from two sources: uptake of yolk components from the retained egg (lecithotrophy) and transfer of nutrients from the maternal circulation via the placenta (placentotrophy). Although net placentotrophy in this species is indicated by the observation that the neonate contains 1.7 times more dry matter than the egg, the placental transfer of lipid has not been previously demonstrated. Lipid analysis was performed on newly ovulated eggs and on neonates. The weight of total lipid per neonate (8.2+/-0.5 mg) is significantly (P=0.049) greater than that in the egg (6.8+/-0.4 mg), indicating that the placenta must contribute some lipid to the fetus. On the assumption that 50% of the lipid delivered to the fetus from either source is oxidized for energy, it is calculated that the placenta accounts for 58.5% of the fetal lipid requirements, with the remaining 41.5% being derived from the egg. The fatty acid compositions of the triacylglycerol and phospholipid recovered in the neonatal tissue differ substantially from those of the egg. In particular, the proportions of 18:2n-6 and 18:3n-3 are far lower in the neonatal lipids compared with the egg lipids. On the other hand, the proportion of 22:6n-3 in the phospholipid of the neonate is six times higher than in the phospholipid of the egg. The absolute amount (mg) of 22:6n-3 recovered in the total lipid of the neonate is 3.8 times greater than the amount initially present in the egg. By comparison, the amount of total fatty acid in neonatal lipid is 1.2 times greater than the amount in the egg. Thus, there is a preferential use of 22:6n-3 for tissue phospholipid synthesis during development. We conclude that there is net transfer of fatty acids across the placenta to the fetus of P. entrecasteauxii and a high degree of selectivity in the use of the various fatty acids for fetal tissue lipid synthesis.
在胎生蜥蜴伪莫氏蜥（Pseudemoia entrecasteauxii）的妊娠期，胎儿从两个来源获取营养：从留存的卵中摄取卵黄成分（卵黄营养）以及通过胎盘从母体循环中转移营养（胎盘营养）。尽管通过观察发现该物种的新生儿干物质含量比卵多1.7倍，表明存在净胎盘营养，但此前尚未证实脂质通过胎盘的转移。对新排出的卵和新生儿进行了脂质分析。每个新生儿的总脂质重量（8.2±0.5毫克）显著高于卵中的总脂质重量（6.8±0.4毫克）（P = 0.049），这表明胎盘必定为胎儿提供了一些脂质。假设从任一来源输送给胎儿的脂质中有50%被氧化以提供能量，经计算胎盘占胎儿脂质需求的58.5%，其余41.5%来自卵。新生儿组织中回收的三酰甘油和磷脂的脂肪酸组成与卵中的脂肪酸组成有很大差异。特别是，与卵脂质相比，新生儿脂质中18:2n - 6和18:3n - 3的比例要低得多。另一方面，新生儿磷脂中22:6n - 3的比例比卵磷脂中的比例高六倍。在新生儿总脂质中回收的22:6n - 3的绝对量（毫克）比卵中最初存在的量高3.8倍。相比之下，新生儿脂质中的总脂肪酸量比卵中的总脂肪酸量高1.2倍。因此，在发育过程中，22:6n - 3被优先用于组织磷脂合成。我们得出结论，脂肪酸通过胎盘向伪莫氏蜥胎儿进行净转移，并且在胎儿组织脂质合成中对各种脂肪酸的使用具有高度选择性。
