Department of Nutritional Sciences, University of Wisconsin, Madison, WI 53706, USA.
Exp Biol Med (Maywood). 2010 Jan;235(1):23-31. doi: 10.1258/ebm.2009.009262.
The dietary selenium recommendation for turkeys of 0.2 microg Se/g is higher than for many other species. Liver glutathione peroxidase-1 (Gpx1) activity levels determined using hydrogen peroxide (H(2)O(2)) in previous studies suggest that 0.2 microg Se/g may still be too low and that some of this Gpx1 activity might be due to phospholipid hydroperoxide Gpx (Gpx4). Thus we separated Gpx1 from Gpx4 by chromatography, demonstrated that 47% of the H(2)O(2) activity in Se-adequate turkey liver was due to Gpx4, and determined a factor for calculation of each activity. Day-old male poults were fed an Se-deficient torula diet (0.007 microg Se/g) supplemented with graded levels of Se (0-0.5 microg Se/g) for 27 days. Final body weights indicated a minimum Se requirement for growth of 0.05 microg Se/g. The liver had the highest Gpx4 activity in Se-adequate poults, and Gpx4 activity in Se-deficient liver decreased to 5% of Se-adequate levels, with an Se requirement of 0.29 microg Se/g. Liver Gpx1, gizzard Gpx1 and gizzard Gpx4 activities also had Se requirements of 0.28-0.30 microg Se/g, collectively yielding an Se requirement of 0.3 microg Se/g, which is three times higher than the requirements found in comparable rodent studies. We also sequenced partial cDNA clones for turkey Gpx1 (GQ502186) and Gpx4 (GQ502187), and found >60% identity with rodents and humans and >90% identity with chickens. Ribonuclease protection analysis showed that Gpx4 mRNA levels decrease substantially in Se-deficient turkey liver, unlike in rodents. These underlying differences in selenoprotein molecular biology may explain the elevated dietary Se requirements of turkeys.
火鸡的膳食硒推荐量为 0.2μg Se/g，高于许多其他物种。先前使用过氧化氢 (H2O2) 测定的肝脏谷胱甘肽过氧化物酶-1 (Gpx1) 活性水平表明，0.2μg Se/g 可能仍然过低，并且这种 Gpx1 活性的一部分可能归因于磷脂氢过氧化物 Gpx (Gpx4)。因此，我们通过色谱法将 Gpx1 与 Gpx4 分离，证明在 Se 充足的火鸡肝脏中，47%的 H2O2 活性归因于 Gpx4，并确定了每种活性的计算因子。1 日龄雄性雏火鸡饲喂缺乏硒的酵母饲料（0.007μg Se/g），并用 0-0.5μg Se/g 的 Se 补充 27 天。最终体重表明生长的最低 Se 需要量为 0.05μg Se/g。Se 充足的雏火鸡肝脏中的 Gpx4 活性最高，而 Se 缺乏的肝脏中的 Gpx4 活性降低至 Se 充足水平的 5%，需要 0.29μg Se/g。肝脏 Gpx1、肌胃 Gpx1 和肌胃 Gpx4 活性也需要 0.28-0.30μg Se/g 的 Se，总需要量为 0.3μg Se/g，是可比啮齿动物研究中发现的需要量的三倍。我们还对火鸡 Gpx1 (GQ502186) 和 Gpx4 (GQ502187) 的部分 cDNA 克隆进行了测序，发现与啮齿动物和人类的相似度>60%，与鸡的相似度>90%。核糖核酸酶保护分析表明，与啮齿动物不同，在 Se 缺乏的火鸡肝脏中，Gpx4 mRNA 水平大幅下降。这些在硒蛋白分子生物学方面的潜在差异可能解释了火鸡对膳食 Se 的高需求。
