Rengasamy A, Johns R A
Department of Anesthesiology, University of Virginia Health Sciences Center, Charlottesville, USA.
J Pharmacol Exp Ther. 1996 Jan;276(1):30-3.
Biosynthesis of nitric oxide (NO) requires L-arginine and molecular oxygen. Although the apparent Km values for L-arginine of NO synthase isoforms have been reported, the apparent Km values for oxygen are unknown. Low oxygen tension has been shown to attenuate NO synthase activity and NO-dependent vascular relaxation. We investigated the effect of different concentrations of oxygen on NO synthase activity of bovine brain, cultured bovine aortic endothelial cells and RAW 264.7 macrophages. The apparent Km values for oxygen were 23.2 +/- 2.8, 7.7 +/- 1.6 and 6.3 +/- 0.9 microM for the brain, endothelial and macrophage NO synthases, respectively. This suggests that pathophysiological conditions involving a decrease in tissue oxygen concentration may attenuate NO production.
一氧化氮（NO）的生物合成需要L-精氨酸和分子氧。虽然已经报道了NO合酶同工型对L-精氨酸的表观Km值，但氧的表观Km值尚不清楚。低氧张力已被证明会减弱NO合酶活性和NO依赖性血管舒张。我们研究了不同浓度的氧对牛脑、培养的牛主动脉内皮细胞和RAW 264.7巨噬细胞中NO合酶活性的影响。脑、内皮和巨噬细胞NO合酶的氧表观Km值分别为23.2±2.8、7.7±1.6和6.3±0.9微摩尔。这表明涉及组织氧浓度降低的病理生理状况可能会减弱NO的产生。
