Boon L, Meijer A J
E. C. Slater Institute for Biochemical Research, University of Amsterdam, The Netherlands.
Eur J Biochem. 1991 Jan 30;195(2):455-7. doi: 10.1111/j.1432-1033.1991.tb15725.x.
Perfusion of rat liver had led to the suggestion that oxygen tension, rather than the distribution of enzymes of urea synthesis, plays a key role in the regulation of urea synthesis in the periportal and pericentral areas of the liver lobule [F. W. Kari, H. Yoshihara and R. G. Thurman (1987) Eur. J. Biochem. 163, 1-7]. We have directly tested the effect of oxygen concentration on ureogenesis under steady-state conditions in isolated hepatocytes perifused with physiological concentrations of ammonia. We found that ureogenesis is independent of the oxygen concentration. Only at oxygen concentrations below 25 microM (which is below the oxygen concentration in liver) was urea synthesis decreased. This was because insufficient production of ATP led to decreased flux through carbamoyl-phosphate synthase. It is concluded that oxygen does not control urea synthesis.
大鼠肝脏灌注实验表明，在肝小叶的门周和中央周围区域，尿素合成的调节中起关键作用的是氧张力，而非尿素合成酶的分布[F. W. 卡里、H. 吉原和R. G. 瑟曼（1987年）《欧洲生物化学杂志》163卷，1 - 7页]。我们在稳定状态下，对用生理浓度氨进行灌流的分离肝细胞，直接测试了氧浓度对尿素生成的影响。我们发现尿素生成与氧浓度无关。只有在氧浓度低于25微摩尔（低于肝脏中的氧浓度）时，尿素合成才会减少。这是因为ATP生成不足导致通过氨甲酰磷酸合成酶的通量降低。结论是氧并不控制尿素合成。
