Stewart P M, Batshaw M, Valle D, Walser M
Am J Physiol. 1981 Oct;241(4):E310-5. doi: 10.1152/ajpendo.1981.241.4.E310.
Cats given a single arginine-free meal have been reported to develop severe hyperammonemia, attributed to impaired function of ornithine aminotransferase (OAT). We found that cats that developed hyperammonemia following an arginine-free meal had low hepatic ornithine levels. However, the average sum of hepatic ornithine plus arginine plus citrulline rose, indicating that some ornithine synthesis via OAT took place, and hyperammonemia failed to occur in cats with higher hepatic ornithine levels. OAT activity and kinetic constants were comparable to values reported in the rat. Furthermore, dietary supplementation with ornithine caused only occasional and transient hyperornithinemia. Thus, OAT can function in the cat. The Ka of N-acetylglutamate (AGA) synthetase for arginine was 5 times higher in cats than in rats, but AGA content and citrullinogenesis by intact mitochondria were the same following arginine-free or arginine-containing meals. Other kinetic parameters of AGA synthetase and carbamoylphosphate synthetase were similar to values in the rat. We conclude that low levels of hepatic ornithine are probably responsible for making some cats susceptible to hyperammonemia following this stimulus.
据报道，给猫喂食一顿不含精氨酸的食物后，它们会出现严重的高氨血症，这归因于鸟氨酸转氨酶（OAT）功能受损。我们发现，在喂食不含精氨酸的食物后出现高氨血症的猫，其肝脏鸟氨酸水平较低。然而，肝脏中鸟氨酸、精氨酸和瓜氨酸的平均总量有所上升，这表明通过OAT发生了一些鸟氨酸合成，并且在肝脏鸟氨酸水平较高的猫中未出现高氨血症。OAT活性和动力学常数与大鼠报道的值相当。此外，用鸟氨酸进行饮食补充仅偶尔导致短暂的高鸟氨酸血症。因此，OAT在猫体内可以发挥作用。猫体内N - 乙酰谷氨酸（AGA）合成酶对精氨酸的Ka值比大鼠高5倍，但在喂食不含精氨酸或含精氨酸的食物后，AGA含量以及完整线粒体的瓜氨酸生成量是相同的。AGA合成酶和氨甲酰磷酸合成酶的其他动力学参数与大鼠的值相似。我们得出结论，肝脏中鸟氨酸水平较低可能是导致一些猫在受到这种刺激后易患高氨血症的原因。
