Plaut K, Maple R L, Wade C E, Baer L A, Ronca A E
University of Vermont, Burlington, VT 05405, USA.
J Appl Physiol (1985). 2003 Dec;95(6):2350-4. doi: 10.1152/japplphysiol.00287.2003. Epub 2003 Aug 15.
Mammary metabolic activity in pregnant rats is significantly increased in response to spaceflight. To determine whether changes in mammary metabolism are related to gravity load, we exposed pregnant rats to hypergravity and measured mammary metabolic activity. From days 11-20 of gestation (G), animals were centrifuged (20 rpm; 1.5, 1.75, or 2.0 x gravity) or were maintained at 1 G. On G20, five rats from each group were removed from the centrifuge and euthanized. The remaining dams (n = 5/treatment) were housed at 1 G until parturition. After 2 h of nursing by the pups, the postpartum dams were euthanized (G22). Glucose oxidation to CO2 and incorporation into lipids was measured. Mammary glands from dams euthanized on G20 revealed a strong negative correlation between metabolic rate and increased G load. Approximately 98% of the variation in glucose oxidation and 94% of the variation in glucose incorporation into lipids can be accounted for by differences in G load. Differences in metabolic activity disappeared in the postpartum dams. When we combined previous data from the microgravity with hypergravity environments and plotted the ratio of mammary metabolic rate vs. G load, there was a significant exponential relationship (r2 = 0.99). These data demonstrate a remarkable continuum of response across the microgravity and hypergravity environments and support the concept that gravitational load influences mammary tissue metabolism.
怀孕大鼠的乳腺代谢活动会因太空飞行而显著增加。为了确定乳腺代谢的变化是否与重力负荷有关，我们将怀孕大鼠暴露于超重环境中并测量乳腺代谢活动。在妊娠（G）的第11至20天，将动物进行离心处理（20转/分钟；1.5、1.75或2.0倍重力）或保持在1倍重力环境。在G20时，从每组中取出五只大鼠，将其从离心机中取出并实施安乐死。其余的母鼠（每组n = 5）在1倍重力环境下饲养直至分娩。在幼崽哺乳2小时后，对产后母鼠实施安乐死（G22）。测量葡萄糖氧化为二氧化碳以及转化为脂质的情况。对在G20时实施安乐死的母鼠的乳腺进行检测发现，代谢率与增加的重力负荷之间存在很强的负相关。重力负荷的差异可以解释约98%的葡萄糖氧化变化以及约94%的葡萄糖转化为脂质的变化。产后母鼠的代谢活动差异消失。当我们将之前来自微重力和超重环境的数据结合起来，并绘制乳腺代谢率与重力负荷的比值时，发现存在显著的指数关系（r2 = 0.99）。这些数据表明在微重力和超重环境中存在显著的连续反应，并支持重力负荷影响乳腺组织代谢这一概念。
