Grigor M R, Allan J E, Carrington J M, Carne A, Geursen A, Young D, Thompson M P, Haynes E B, Coleman R A
J Nutr. 1987 Jul;117(7):1247-58. doi: 10.1093/jn/117.7.1247.
Lactating rats have been fed either a protein-restricted diet (10 vs. 20% casein in the control diet) or the control diet at 80, 60 and 40% of the voluntary intake for 7 d from d 7 of lactation. Food consumption, changes in maternal live weight, litter live weight gain and the mass of several maternal tissues were determined together with the activity of several mammary and liver enzymes, including 10 that are essential for fatty acid and complex lipid synthesis. Milk production was estimated from the litter weight gain and litter weight. Lactating rats fed the 20% protein diet ad libitum consumed three times that of nonlactating rats; their liver and kidney masses were significantly higher and their adipose mass was lower. The livers of the lactating rats were fatty, containing 118 mg lipid/g compared with 42 mg/g for the nonlactating rats. Lactating rats fed either the protein-restricted diet or the control diet at 40 and 60% of the ad libitum intake of the control diet had lower mammary, liver and kidney masses than rats consuming the control diet ad libitum. Both protein and food restriction led to lower rates of milk production than those of ad libitum-fed control rats as evidenced by the decrease in litter live weight gains. The concentrations of total lipid, total protein and lactose in milk were not affected by these dietary treatments. The concentration of alpha-lactalbumin in milk of rats fed the low protein diet was, however, lower than that in the milk of all rats receiving the control diet, irrespective of intake. Consumption of the restricted diets resulted in only small changes in specific activities (mu/mg protein) of 15 mammary enzymes. In the livers, lactation led to higher specific activities of all four soluble lipogenic enzymes examined but did not affect the particulate enzymes involved in complex lipid synthesis. The dietary restrictions resulted in lower specific activities of the soluble enzymes compared with those of the lactating rats consuming the control diet ad libitum without affecting the particulate enzymes. Total activities of these enzymes were, however, lower than those for the control rats as a result of the smaller liver mass in the rats receiving the restricted diets.
从哺乳期第7天开始，给哺乳大鼠喂食蛋白质限制饮食（对照饮食中酪蛋白含量为10%，而对照饮食中酪蛋白含量为20%）或按对照饮食自由摄入量的80%、60%和40%喂食对照饮食，持续7天。测定食物消耗量、母体体重变化、窝仔体重增加量以及几个母体组织的质量，同时测定几种乳腺和肝脏酶的活性，包括对脂肪酸和复合脂质合成至关重要的10种酶。根据窝仔体重增加量和窝仔体重估算产奶量。自由采食20%蛋白质饮食的哺乳大鼠的食物消耗量是非哺乳大鼠的三倍；它们的肝脏和肾脏质量显著更高，脂肪质量更低。哺乳大鼠的肝脏富含脂肪，每克肝脏含118毫克脂质，而非哺乳大鼠每克肝脏含42毫克脂质。与自由采食对照饮食的大鼠相比，喂食蛋白质限制饮食或按对照饮食自由摄入量的40%和60%喂食对照饮食的哺乳大鼠的乳腺、肝脏和肾脏质量更低。蛋白质和食物限制均导致产奶率低于自由采食对照饮食的大鼠，窝仔体重增加量减少证明了这一点。这些饮食处理对牛奶中总脂质、总蛋白质和乳糖的浓度没有影响。然而，喂食低蛋白饮食的大鼠所产牛奶中α-乳白蛋白的浓度低于所有接受对照饮食的大鼠所产牛奶中的浓度，与摄入量无关。食用限制饮食仅导致15种乳腺酶的比活性（μ/毫克蛋白质）发生微小变化。在肝脏中，哺乳导致所检测的所有四种可溶性脂肪生成酶的比活性更高，但不影响参与复合脂质合成的颗粒酶。与自由采食对照饮食的哺乳大鼠相比，饮食限制导致可溶性酶的比活性更低，但不影响颗粒酶。然而，由于接受限制饮食的大鼠肝脏质量较小，这些酶的总活性低于对照大鼠。
