Department of Zoology, University of Otago, Dunedin, New Zealand.
Fisheries Department, Faculty of Natural Resources, University of Guilan, Sowmeh Sara, Guilan, Iran.
Am J Physiol Regul Integr Comp Physiol. 2020 Sep 1;319(3):R376-R386. doi: 10.1152/ajpregu.00364.2019. Epub 2020 Aug 5.
The present study was conducted to understand key biochemical, physiological, and molecular changes associated with ovarian growth and with lipid transfer and/or accumulation into the ovary during oogenesis in captive beluga sturgeon. Plasma levels of triacylglycerides, cholesterol, phospholipid, and sex steroid hormones were determined and all were found to increase notably throughout development from the perinucleolar to the tertiary yolk stage. Using fast protein liquid chromatography, we recognized three major lipoprotein peaks in chromatograms from all samples. These peaks were characterized as containing very low-density lipoprotein (Vldl), low-density lipoprotein/high-density lipoprotein (Ldl/Hdl), and plasma proteins. While Ldl/Hdl represented the most abundant lipoprotein fraction, the relative abundance of different lipoprotein classes did not change with the stage of oogenesis. Eluted lipoproteins were separated using sodium dodecyl-sulfate polyacrylamide gel electrophoresis and sequenced. The peptide sequence spectra for 66-kDa, 205-kDa, 29-kDa, and 70-kDa bands matched with albumin, vitellogenin (Vtg) AB2b, immunoglobulin light-chain precursor, and immunoglobulin heavy-chain, respectively. The large amount of albumin in the plasma protein peak and the confined presence of Vtg AB2b to within Ldl/Hdl reinforce the lipoprotein classification. Lastly, transcript levels of genes encoding ovarian lipoprotein lipase (), apolipoprotein E (), very low-density lipoprotein receptors (), and low-density lipoprotein receptor-related protein 8-like () were estimated using quantitative RT-PCR. The high mRNA levels of , , and lipoprotein receptors and in previtellogenic females suggest that sturgeon oocytes need to be prepared to accept and traffic Vtg and lipids internally, before the start of vitellogenesis.
本研究旨在了解与卵巢生长以及卵母细胞发生过程中脂质转移和/或积累到卵巢相关的关键生化、生理和分子变化。测定了血浆中三酰甘油、胆固醇、磷脂和性激素水平，结果发现，从核周体到三级卵黄期，所有这些水平在发育过程中都显著增加。使用快速蛋白液相色谱法，我们在所有样品的图谱中识别出三个主要的脂蛋白峰。这些峰被特征化为含有极低密度脂蛋白 (Vldl)、低密度脂蛋白/高密度脂蛋白 (Ldl/Hdl) 和血浆蛋白。虽然 Ldl/Hdl 是最丰富的脂蛋白部分，但不同脂蛋白类别的相对丰度不会随卵母细胞发生的阶段而变化。洗脱的脂蛋白使用十二烷基硫酸钠聚丙烯酰胺凝胶电泳分离并测序。66 kDa、205 kDa、29 kDa 和 70 kDa 带的肽序列图谱分别与白蛋白、卵黄蛋白 AB2b、免疫球蛋白轻链前体和免疫球蛋白重链匹配。血浆蛋白峰中大量的白蛋白和 Ldl/Hdl 中仅存在卵黄蛋白 AB2b，这加强了脂蛋白的分类。最后，使用定量 RT-PCR 估计编码卵巢脂蛋白脂肪酶 ()、载脂蛋白 E ()、极低密度脂蛋白受体 () 和低密度脂蛋白受体相关蛋白 8 样 () 的基因的转录水平。在预卵母细胞期雌性中， 、 和脂蛋白受体 和 的高 mRNA 水平表明，在卵黄发生开始之前，鲟鱼卵母细胞需要准备接受和内部转运卵黄蛋白和脂质。
