Grigor M R, Thompson M P
J Nutr. 1987 Apr;117(4):748-53. doi: 10.1093/jn/117.4.748.
Lactating rats consuming a control diet (20% casein) ad libitum and kept on a 12-h light-dark cycle produced milk during the dark phase at a rate 50% greater than that during the light period. Diurnal variations in the food consumptions of these animals, maternal live weights and litter weight gains were also observed. This diurnal variation with respect to milk production and food consumption appears to be abolished by feeding a low protein (10% casein) diet. However, the variation was amplified when the amount of the control diet was restricted to 25 g/d and made available at the middark period; this was probably related to the meal-feeding behavior of these rats because they consumed all their food within 6 h after it was made available. The rates of fatty acid synthesis in the mammary glands, livers and adipose tissue measured in vivo from [3H]H2O incorporation also varied diurnally with maximal rates at the middark period. Similar rates were obtained for the rats receiving restricted amounts of the control diet measured in the feeding period, whereas the values for the rats fed the low protein diet in the dark period tended to be significantly lower. The milk fatty acids were also analyzed, and whereas no diurnal differences were detected in the samples taken from control rats, a marked reduction in the proportion of the medium-chain acids was observed in the samples from rats receiving restricted amounts of the control diet taken immediately before the normal feeding period.
随意进食对照饮食（20%酪蛋白）并维持12小时明暗循环的泌乳大鼠，在黑暗期产奶速度比光照期快50%。还观察到了这些动物的食物消耗、母体体重和窝仔体重增加的昼夜变化。喂食低蛋白（10%酪蛋白）饮食似乎消除了产奶量和食物消耗方面的这种昼夜变化。然而，当对照饮食量限制为25克/天并在黑暗中期提供时，这种变化被放大了；这可能与这些大鼠的进食行为有关，因为它们在食物提供后6小时内就吃光了所有食物。通过[3H]H2O掺入在体内测量的乳腺、肝脏和脂肪组织中的脂肪酸合成速率也随昼夜变化，在黑暗中期达到最大值。在进食期对接受对照饮食量受限的大鼠进行测量时得到了类似的速率，而在黑暗期喂食低蛋白饮食的大鼠的值往往明显较低。还对乳脂肪酸进行了分析，虽然从对照大鼠采集的样本中未检测到昼夜差异，但在正常喂食期前立即采集的接受对照饮食量受限的大鼠样本中，中链酸的比例明显降低。
