Herrera E, Knopp R H, Freinkel N
J Clin Invest. 1969 Dec;48(12):2260-72. doi: 10.1172/JCI106192.
The effects of late pregnancy on metabolic fuels, liver composition, gluconeogenesis, and nitrogen metabolism have been examined in fed and fasted rats. Plasma free fatty acid (FFA) and immunoreactive insulin (IRI) are greater and glucose and ketones are lower in fed 19-day pregnant than they are in agematched virgin rats. A 48 hr fast elicits greater increases in FFA and ketones and more profound reductions in glucose in the pregnant rats and obliterates the differences in IRI. Fetal weight is not modified by such fasting but maternal weight losses exceed that of the nongravid rats. Livers from rats 19 days pregnant contain more and larger hepatocytes. Per mumole hepatic deoxyribonucleic acid (DNA)-phosphorus, water and protein are more abundant, whereas glycogen is unaffected. Livers from fed pregnant rats contain more lipid phosphorus and less neutral lipid fatty acid. After a 48 hr fast, hepatic steatosis supervenes in gravid animals due to accumulated neutral fat. The contents of hepatic acetyl-coenzyme A (CoA) and citric acid are not different in fed pregnant and virgin rats but are greater in the pregnant rats after fasting. Formation of glucose-(14)C and glycogen-(14)C from administered pyruvate-(14)C are the same in fed pregnant and virgin rats, but greater in the pregnant ones after a 24 or 48 hr fast. Pregnancy does not affect creatinine excretion, and urinary urea is not different in fed pregnant, virgin, and postpartum animals. Contrariwise, more nitrogen, potassium, and phosphorus are excreted by the pregnant animals during a 2 day fast. The increment in urinary nitrogen is due largely to urea on the 1st day, whereas heightened ammonia accounts for half the increase on the 2nd and correlates with the enhanced ketonuria. Muscle catabolism, gluconeogenesis, and diversion to fat are activated more rapidly and to a greater degree when food is withheld during late gestation in the rat. These catabolic propensities are restrained in the fed state. The capacity for "accelerated starvation" may confer survival benefit upon an intermittently eating mother in the presence of a continuously feeding fetus.
已在喂食和禁食的大鼠中研究了妊娠晚期对代谢燃料、肝脏组成、糖异生和氮代谢的影响。与年龄匹配的未孕大鼠相比，喂食的妊娠19天大鼠的血浆游离脂肪酸（FFA）和免疫反应性胰岛素（IRI）更高，而葡萄糖和酮类更低。禁食48小时会使妊娠大鼠的FFA和酮类增加更多，葡萄糖降低更显著，并消除了IRI的差异。这种禁食不会改变胎儿体重，但母体体重减轻超过未孕大鼠。妊娠19天大鼠的肝脏含有更多且更大的肝细胞。每微摩尔肝脱氧核糖核酸（DNA）-磷中，水和蛋白质含量更丰富，而糖原不受影响。喂食的妊娠大鼠肝脏含有更多的脂质磷和更少的中性脂质脂肪酸。禁食48小时后，妊娠动物肝脏因中性脂肪积累而出现脂肪变性。喂食的妊娠大鼠和未孕大鼠肝脏中乙酰辅酶A（CoA）和柠檬酸的含量没有差异，但禁食后妊娠大鼠肝脏中的含量更高。给予丙酮酸-（14）C后，喂食的妊娠大鼠和未孕大鼠生成葡萄糖-（14）C和糖原-（14）C的情况相同，但禁食24或48小时后，妊娠大鼠生成的更多。妊娠不影响肌酐排泄，喂食的妊娠大鼠、未孕大鼠和产后动物的尿尿素没有差异。相反，在禁食2天期间，妊娠动物排泄更多的氮、钾和磷。尿氮增加在第1天主要归因于尿素，而第2天氨增加占增加量的一半，且与酮尿增加相关。在大鼠妊娠晚期禁食时，肌肉分解代谢、糖异生和向脂肪的转化比在进食状态下更迅速且程度更大地被激活。这些分解代谢倾向在进食状态下受到抑制。“加速饥饿”的能力可能会在存在持续进食胎儿的情况下，为间歇性进食的母亲带来生存益处。
