Hayase K, Yonekawa G, Yoshida A
Department of Home Economics, Aichi University of Education, Japan.
J Nutr. 1993 Feb;123(2):253-8. doi: 10.1093/jn/123.2.253.
The purpose of the present study was to determine whether the regulation of urea synthesis was mediated through the activation of N-acetylglutamate synthesis by arginine and whether the concentration of glutamate or activity of N-acetylglutamate synthetase might control N-acetylglutamate concentration when the thyroid status was manipulated. Three groups of rats were given 6-propyl-2-thiouracil (PTU, thyroid inhibitor) without triiodothyronine (T3) treatment, treated with PTU + T3 or treated with neither PTU nor T3 (control). Urinary excretion of urea, liver concentration of N-acetylglutamate and plasma concentration of arginine in rats given PTU + T3 were significantly lower than in rats given PTU alone. Liver concentration of N-acetyl-glutamate was correlated with plasma concentration of arginine (r = 0.842, P < 0.001). The activity of N-acetylglutamate synthetase and glutamate concentration in liver of the PTU + T3-treated group were significantly higher than in the group treated with PTU alone. Arginine administration (0.5 mmol/100 g body wt) elevated the liver concentration of N-acetylglutamate in all three groups. The results suggest that the greater concentration of arginine in the hypothyroid (PTU alone) rats is likely to increase the N-acetylglutamate concentration and stimulate urea synthesis.
本研究的目的是确定尿素合成的调节是否通过精氨酸激活N-乙酰谷氨酸合成来介导，以及当甲状腺状态受到控制时，谷氨酸浓度或N-乙酰谷氨酸合成酶的活性是否可能控制N-乙酰谷氨酸的浓度。将三组大鼠分别给予6-丙基-2-硫氧嘧啶（PTU，甲状腺抑制剂）且不进行三碘甲状腺原氨酸（T3）治疗、给予PTU + T3治疗或既不给予PTU也不给予T3治疗（对照组）。给予PTU + T3的大鼠的尿素尿排泄量、肝脏N-乙酰谷氨酸浓度和血浆精氨酸浓度显著低于仅给予PTU的大鼠。肝脏N-乙酰谷氨酸浓度与血浆精氨酸浓度相关（r = 0.842，P < 0.001）。PTU + T3治疗组大鼠肝脏中N-乙酰谷氨酸合成酶的活性和谷氨酸浓度显著高于仅给予PTU治疗的组。给予精氨酸（0.5 mmol/100 g体重）可提高所有三组大鼠肝脏中N-乙酰谷氨酸的浓度。结果表明，甲状腺功能减退（仅给予PTU）大鼠中较高的精氨酸浓度可能会增加N-乙酰谷氨酸浓度并刺激尿素合成。
