Wiechetek M, Souffrant W B, Garwacki S
Int J Biochem. 1986;18(7):653-7. doi: 10.1016/0020-711x(86)90296-x.
Utilization of N from 15NH4Cl and [15N]alanine for urea synthesis in hepatocytes isolated from fed and 24 hr starved rats was investigated. In hepatocytes isolated from fed rats, 54 and 65% of the added [15N]ammonia was utilized for urea synthesis in the presence of 0.5 and 2.0 mM NH4Cl, respectively. This utilization of [15N]ammonia in hepatocytes from starved rats was 2-fold lower. The amount of urea synthetized from endogenous sources was, in the presence of 0.5 and 2.0 mM NH4Cl, about 44 and 60% higher than in the control conditions (without NH4Cl). The considerable amount of added ammonia (30-44%) was utilized in processes other than urea synthesis. Alanine markedly diminished the utilization of 15N from NH4Cl in hepatocytes from both fed and starved rats. In these conditions (NH4Cl present), alanine significantly increased the urea formation in hepatocytes from starved rats and failed to affect the urea production in hepatocytes from fed rats. On the basis of 15N determination, it was concluded that both NH4Cl and alanine caused an increase in the utilization of nitrogen from endogenous sources in rat hepatocytes. This conclusion is in contrast with the results based only on the changes in ammonia and urea concentrations.
研究了来自喂食和饥饿24小时大鼠的肝细胞利用15NH4Cl和[15N]丙氨酸中的氮进行尿素合成的情况。在来自喂食大鼠的肝细胞中，分别在存在0.5 mM和2.0 mM NH4Cl的情况下，添加的[15N]氨中有54%和65%用于尿素合成。饥饿大鼠肝细胞中[15N]氨的这种利用率低2倍。在存在0.5 mM和2.0 mM NH4Cl的情况下，内源性来源合成的尿素量比对照条件（无NH4Cl）高约44%和60%。相当数量的添加氨（30 - 44%）用于尿素合成以外的过程。丙氨酸显著降低了来自喂食和饥饿大鼠的肝细胞中NH4Cl的15N利用率。在这些条件下（存在NH4Cl），丙氨酸显著增加了饥饿大鼠肝细胞中的尿素形成，而对喂食大鼠肝细胞中的尿素产生没有影响。基于15N测定，得出结论：NH4Cl和丙氨酸都导致大鼠肝细胞中内源性氮利用率增加。这一结论与仅基于氨和尿素浓度变化的结果相反。
