Kato H, Mizutani-Funahashi M, Shiosaka S, Nakagawa H
J Nutr. 1978 Jul;108(7):1071-7. doi: 10.1093/jn/108.7.1071.
The circadian rhythms of the urea concentrations in urine, serum, and liver and their generation mechanism were investigated. When rats were allowed to eat freely, the urea concentration and the total urea content of the urine were higher during the night than during the day-time. Consistent with these findings, the urea concentrations in the liver and serum had circadian rhythms with the highest values at 0200 hours and the lowest values at 1400 hours. The amplitude of the rhythm increased with increase in the dietary protein (casein) content. Of the five urea cycle enzymes in the liver, only argininosuccinate synthetase showed fluctuation in activity, and this had the same pattern as the circadian rhythms of urea concentrations. These findings suggest that the circadian rhythm of argininosuccinate synthetase in the liver might be directly responsible for the rhythms of change in urea concentrations in the liver, blood and urine. The circadian increase in enzyme activity was inhibited by cycloheximide, but not by actinomycin D.
研究了尿液、血清和肝脏中尿素浓度的昼夜节律及其产生机制。当大鼠自由进食时，夜间尿液中的尿素浓度和总尿素含量高于白天。与这些发现一致，肝脏和血清中的尿素浓度具有昼夜节律，在02:00时最高，在14:00时最低。节律的幅度随着膳食蛋白质（酪蛋白）含量的增加而增加。在肝脏中的五种尿素循环酶中，只有精氨琥珀酸合成酶的活性有波动，且与尿素浓度的昼夜节律模式相同。这些发现表明，肝脏中精氨琥珀酸合成酶的昼夜节律可能直接导致肝脏、血液和尿液中尿素浓度变化的节律。酶活性的昼夜增加受到环己酰亚胺的抑制，但不受放线菌素D的抑制。
