Takahashi K, Matsumoto T, Kubo S, Haraoka M, Tanaka M, Kumazawa J
Department of Urology, Faculty of Medicine, Kyushu University, Fukuoka, Japan.
J Urol. 1994 Nov;152(5 Pt 1):1622-5. doi: 10.1016/s0022-5347(17)32491-6.
Hyperosmotic environment in the renal medulla seems important for bacterial pyelonephritis because it exerts inhibitory influences upon the function of polymorphonuclear leukocytes (PMN). Urea and NaCl primarily contribute to high osmolarity in the renal medulla. We previously reported that PMN function was actually suppressed in phagocytosis, intracellular bacterial killing and superoxide generation in the hyperosmotic solution of urea and NaCl. In the present report, to verify the mechanism of this inhibitory effect, a kinetic study for NADPH oxidase in the cell membrane, the key enzyme complex of superoxide generation, was carried out in the cell membrane-solubilizing system under the hyperosmotic condition caused by urea or NaCl. Urea directly denaturated NADPH oxidase, and its inhibitory mechanism was reversible and uncompetitive with a decrease in Vmax and Km, while NaCl had no effect upon it, maintaining Lineweaver-Burk plots in the same position as those of the control. This result suggests that urea at least produces an inhibitory effect upon PMN through the direct inactivation of NADPH oxidase, although NaCl was unable to do so.
肾髓质的高渗环境对细菌性肾盂肾炎似乎很重要，因为它对多形核白细胞（PMN）的功能有抑制作用。尿素和氯化钠是肾髓质高渗透压的主要贡献者。我们之前报道过，在尿素和氯化钠的高渗溶液中，PMN的吞噬作用、细胞内细菌杀伤和超氧化物生成功能实际上受到了抑制。在本报告中，为了验证这种抑制作用的机制，在由尿素或氯化钠引起的高渗条件下，在细胞膜增溶系统中对超氧化物生成的关键酶复合物——细胞膜中的NADPH氧化酶进行了动力学研究。尿素直接使NADPH氧化酶变性，其抑制机制是可逆的且为非竞争性，Vmax和Km降低，而氯化钠对其没有影响，Lineweaver-Burk图保持在与对照组相同的位置。该结果表明，尽管氯化钠无法做到，但尿素至少通过直接使NADPH氧化酶失活对PMN产生抑制作用。
