Williams T D
Department of Biological Sciences, Simon Fraser University, 8888 University Drive, Burnaby, British Columbia V5A 1S6, Canada.
Physiol Biochem Zool. 2000 Sep-Oct;73(5):566-73. doi: 10.1086/317748.
Experimental manipulation of reproductive phenotype is a potentially powerful approach for understanding the fitness relationships of traits such as egg size, egg composition, and egg number. In this study, I investigated the effect of the antiestrogen tamoxifen on multiple, estrogen-dependent reproductive traits in female zebra finches (Taeniopygia guttata). Short-term tamoxifen treatment of egg-laying females (two daily injections before laying) had no effect on the timing or the pattern of egg laying compared to sham controls. However, tamoxifen treatment caused (1) a marked, but transient, decrease in egg size; (2) increased within-clutch egg-size variation; (3) a reduction in plasma vitellogenin (VTG) levels; and (4) lower dry yolk and yolk protein content of tamoxifen-treated females. Plasma levels of the second yolk precursor, very low density lipoprotein (VLDL), were not affected by tamoxifen, and tamoxifen appeared to have no effect on oviduct function in egg-laying females. These results are consistent with tamoxifen blocking estrogen receptors in the liver, suppressing VTG production, and decreasing the plasma pool of yolk precursors below a level required to maintain yolk formation at the normal rate. Tamoxifen treatment can therefore be used successfully to manipulate several components of the female reproductive phenotype (egg composition, intraclutch egg-size variation) to further explore the fitness consequences of these traits.
对生殖表型进行实验性操控是理解诸如卵大小、卵成分和卵数量等性状的适合度关系的一种潜在有力方法。在本研究中，我调查了抗雌激素他莫昔芬对雌性斑胸草雀（Taeniopygia guttata）多种雌激素依赖性生殖性状的影响。与假手术对照组相比，对正在产卵的雌性进行短期他莫昔芬处理（产卵前每日注射两次）对产卵时间或模式没有影响。然而，他莫昔芬处理导致：（1）卵大小显著但短暂减小；（2）窝内卵大小变异增加；（3）血浆卵黄蛋白原（VTG）水平降低；（4）接受他莫昔芬处理的雌性的干卵黄和卵黄蛋白含量降低。第二种卵黄前体极低密度脂蛋白（VLDL）的血浆水平不受他莫昔芬影响，并且他莫昔芬似乎对正在产卵的雌性的输卵管功能没有影响。这些结果与他莫昔芬阻断肝脏中的雌激素受体、抑制VTG产生以及将卵黄前体的血浆池降低到维持正常速率的卵黄形成所需水平以下一致。因此，他莫昔芬处理可成功用于操控雌性生殖表型的几个组成部分（卵成分、窝内卵大小变异），以进一步探索这些性状的适合度后果。
