Eppel Gabriela A, Denton Kate M, Malpas Simon C, Evans Roger G
Department of Physiology, Monash University, PO Box 13F, VIC 3800 Clayton, Australia.
Pflugers Arch. 2003 Nov;447(2):205-13. doi: 10.1007/s00424-003-1149-1. Epub 2003 Aug 5.
The mechanisms underlying the relative insensitivity of medullary blood flow (MBF) to sympathetic drive remain unknown. We tested the effects of nitric oxide synthase blockade on regional kidney perfusion responses to electrical renal nerve stimulation (RNS) in pentobarbitone-anaesthetized rabbits. Under control conditions, RNS reduced renal blood flow (RBF), cortical blood flow (CBF) and MBF in a frequency-dependent manner. MBF was always reduced less than CBF or RBF. NG-nitro-L-arginine increased mean arterial pressure (31+/-3 mmHg), reduced RBF (-8+/-1 ml/min) and MBF (-33+/-6 units), enhanced responses to RNS of RBF (from -48+/-6% to -58+/-6% at 2 Hz), CBF (from -38+/-6% to -43+/-4% at 2 Hz) and, particularly at low frequencies, MBF (from +1+/-18% to -32+/-11% at 2 Hz) and potentiated the RBF hyperaemic response following RNS (by 27+/-6% at 4 Hz). When glyceryl trinitrate was co-infused with NG-nitro-L-arginine to restore basal nitrergic tone, responses to RNS and the subsequent hyperaemia were indistinguishable from control. Since resting renovascular tone or perfusion pressure has little impact on MBF responses to RNS, these present observations suggest that NO contributes to the blunted MBF response to RNS. Paradoxically, NO seems to blunt renal hyperaemia following acute RNS-induced ischaemia.
髓质血流（MBF）对交感神经驱动相对不敏感的潜在机制尚不清楚。我们测试了一氧化氮合酶阻断对戊巴比妥麻醉兔肾神经电刺激（RNS）引起的局部肾脏灌注反应的影响。在对照条件下，RNS以频率依赖性方式降低肾血流量（RBF）、皮质血流量（CBF）和MBF。MBF的降低总是小于CBF或RBF。NG-硝基-L-精氨酸升高平均动脉压（31±3 mmHg），降低RBF（-8±1 ml/min）和MBF（-33±6单位），增强RBF（2 Hz时从-48±6%增至-58±6%）、CBF（2 Hz时从-38±6%增至-43±4%）对RNS的反应，尤其是在低频时，增强MBF（2 Hz时从+1±18%降至-32±11%）对RNS的反应，并增强RNS后RBF的充血反应（4 Hz时增加27±6%）。当硝酸甘油与NG-硝基-L-精氨酸共同输注以恢复基础硝化张力时，对RNS的反应和随后的充血与对照无明显差异。由于静息肾血管张力或灌注压力对MBF对RNS的反应影响很小，目前的这些观察结果表明，NO促成了MBF对RNS反应的减弱。矛盾的是，NO似乎减弱了急性RNS诱导的缺血后的肾充血。
