Hanai Miho, Yoshikuni Miko, Hikita Haruna
Department of Nutrition and Life Science, Kanagawa Institute of Technology.
J Nutr Sci Vitaminol (Tokyo). 2017;63(6):372-378. doi: 10.3177/jnsv.63.372.
The purpose of this study was to clarify the effects of dietary protein levels on protein nutritional status in rats kept under constant darkness. Thirty-six 4-wk-old female rats (F344 strain) were divided into six groups. Each group was given a diet with one of three different protein levels and kept under normal light and dark cycles (7:00-19:00 light period/19:00-7:00 dark period, N group) or under constant darkness (D group) for 4 wk. The protein levels of the diets were 10%, 20%, and 30% casein. The six groups are referred to as the N10%, N20%, N30%, D10%, D20%, and D30% groups. Body weight gain was low in the D groups, and that in the D30% group was much lower than that in the N30% group. The D30% group retained less nitrogen than the N30% group. As for the amount of urinary nitrogen excreted every 4 h, the values for the D-groups were higher than those for the N-groups in the 11:00-15:00 periods, and that for the D30% group was higher than that for the N30% group in the 15:00-19:00 periods, which means that protein catabolism was higher in the D30% group. It was shown that when rats kept under constant darkness were fed a high-protein diet for 4 wk, their nitrogen retention decreased and their protein nutritional state dropped.
本研究的目的是阐明日粮蛋白质水平对处于持续黑暗环境中的大鼠蛋白质营养状况的影响。将36只4周龄雌性大鼠（F344品系）分为6组。每组给予三种不同蛋白质水平之一的日粮，并在正常光照和黑暗周期（光照期7:00 - 19:00/黑暗期19:00 - 7:00，N组）或持续黑暗环境（D组）中饲养4周。日粮的蛋白质水平分别为10%、20%和30%的酪蛋白。这6组分别称为N10%组、N20%组、N30%组、D10%组、D20%组和D30%组。D组的体重增加较低，且D30%组的体重增加远低于N30%组。D30%组保留的氮比N30%组少。至于每4小时排泄的尿氮量，在11:00 - 15:00期间，D组的值高于N组，在15:00 - 19:00期间，D30%组的值高于N30%组，这意味着D30%组的蛋白质分解代谢更高。结果表明，当处于持续黑暗环境中的大鼠喂食高蛋白日粮4周时，它们的氮保留减少，蛋白质营养状态下降。
