Salvante Katrina G, Lin Gina, Walzem Rosemary L, Williams Tony D
Department of Biological Sciences, Simon Fraser University, 8888 University Drive, Burnaby, British Columbia, V5A 1S6, Canada.
J Exp Biol. 2007 Mar;210(Pt 6):1064-74. doi: 10.1242/jeb.02724.
During avian egg production, oestrogen mediates marked increases in hepatic lipid production and changes in the diameter of assembled very-low density lipoprotein (VLDL). A nearly complete shift from generic VLDL ( approximately 70 nm in diameter), which transports lipids to peripheral tissues, to yolk-targeted VLDL (VLDLy) ( approximately 30 nm), which supplies the yolk with energy-rich lipid, has been observed in the plasma of laying domestic fowl. We validated an established dynamic laser scattering technique for a passerine songbird Taeniopygia guttata, the zebra finch, to characterize the dynamics of VLDL particle diameter distribution in relation to egg production. We predicted that non-gallinaceous avian species that have not been selected for maximum egg production would exhibit less dramatic shifts in lipid metabolism during egg production. As predicted, there was considerable overlap between the VLDL particle diameter distributions of laying and non-laying zebra finches. But unexpectedly, non-laying zebra finches had VLDL diameter distributions that peaked at small particles and had relatively few large VLDL particles. As a result, laying zebra finches, in comparison, had diameter distributions that were shifted towards larger VLDL particles. Nevertheless, laying zebra finches, like laying chickens, had larger proportions of particles within proposed VLDLy particle diameter ranges than non-laying zebra finches (e.g. sVLDLy: 50% vs 37%). Furthermore, zebra finches and chickens had similar modal (29.7 nm in both species) and median (32.7 nm vs 29.6 nm) VLDL particle diameters during egg production. Therefore, although zebra finches and chickens exhibited opposing directional shifts in VLDL particle diameter distribution during egg production, the modifications to VLDL particle structure in both species resulted in the realization of a common goal, i.e. to produce and maintain a large proportion of small VLDL particles of specific diameters that are capable of being incorporated into newly forming egg yolks.
在鸟类产蛋过程中，雌激素介导肝脏脂质生成显著增加以及组装好的极低密度脂蛋白（VLDL）直径发生变化。在家养产蛋禽类的血浆中，已观察到从将脂质转运至外周组织的普通VLDL（直径约70纳米）几乎完全转变为向卵黄供应富含能量脂质的靶向卵黄VLDL（VLDLy）（直径约30纳米）。我们验证了一种已确立的动态激光散射技术可用于雀形目鸣禽斑胸草雀，以表征与产蛋相关的VLDL颗粒直径分布动态。我们预测，未被选育以实现最大产蛋量的非鸡形目鸟类在产蛋期间脂质代谢的变化不会那么显著。如预测的那样，产蛋和不产蛋斑胸草雀的VLDL颗粒直径分布有相当大的重叠。但出乎意料的是，不产蛋斑胸草雀的VLDL直径分布在小颗粒处达到峰值，且大VLDL颗粒相对较少。相比之下，产蛋斑胸草雀的直径分布则向较大的VLDL颗粒偏移。尽管如此，与不产蛋斑胸草雀相比，产蛋斑胸草雀在拟议的VLDLy颗粒直径范围内的颗粒比例更高（例如，小VLDLy：50%对37%）。此外，斑胸草雀和鸡在产蛋期间的VLDL颗粒直径的众数（两个物种均为29.7纳米）和中位数（32.7纳米对29.6纳米）相似。因此，尽管斑胸草雀和鸡在产蛋期间VLDL颗粒直径分布呈现相反的方向变化，但两个物种中VLDL颗粒结构的改变都实现了一个共同目标，即产生并维持很大比例的特定直径的小VLDL颗粒，这些颗粒能够被整合到新形成的蛋黄中。
