Yang S, Silldorff E P, Pallone T L
Division of Nephrology, M. S. Hershey Medical Center, Pennsylvania State University, Hershey 17033, USA.
Am J Physiol. 1995 Aug;269(2 Pt 2):H710-6. doi: 10.1152/ajpheart.1995.269.2.H710.
To examine their responsiveness to norepinephrine (NE) and acetylcholine (ACh), outer medullary descending vasa recta (OMDVR) have been dissected from vascular bundles of the rat and perfused in vitro. Abluminal application of NE produced graded vasoconstriction in a concentration range of 10(-9)-10(-6) M. When applied with NE, ACh at concentrations of 10(-8)-10(-5) M dilated NE-preconstricted OMDVR. In contrast, ACh applied in the absence of NE caused vasoconstriction. ACh-induced vasodilation was blocked by addition of the nitric oxide synthase inhibitor N omega-nitro-L-arginine (L-NNA, 2 x 10(-4) M). L-NNA in the absence of ACh enhanced NE-induced vasoconstriction. Supraphysiological (10(-3) M) L-arginine (L-Arg) reversed the effects of L-NNA, and abluminal application of L-NNA alone resulted in OMDVR vasoconstriction. At concentrations of 10(-6)-10(-3) M, abluminal application of L-Arg produced graded vasodilation of NE-constricted OMDVR. These results suggest that adrenergic and cholinergic innervation could influence OMDVR vasomotor tone to modulate total and regional blood flow to the renal medulla. The data also favor a role for the activity of constitutively expressed nitric oxide synthase to modulate OMDVR vasoactivity.
为了研究外髓质下行直小血管（OMDVR）对去甲肾上腺素（NE）和乙酰胆碱（ACh）的反应性，已从大鼠的血管束中分离出OMDVR并进行体外灌注。在10^(-9)-10^(-6) M的浓度范围内，向管腔外施加NE可产生分级血管收缩。当与NE一起应用时，浓度为10^(-8)-10^(-5) M的ACh可使预先由NE收缩的OMDVR舒张。相比之下，在没有NE的情况下应用ACh会导致血管收缩。添加一氧化氮合酶抑制剂Nω-硝基-L-精氨酸（L-NNA，2×10^(-4) M）可阻断ACh诱导的血管舒张。在没有ACh的情况下，L-NNA可增强NE诱导的血管收缩。超生理浓度（10^(-3) M）的L-精氨酸（L-Arg）可逆转L-NNA的作用，单独向管腔外应用L-NNA会导致OMDVR血管收缩。在10^(-6)-10^(-3) M的浓度范围内，向管腔外应用L-Arg可使由NE收缩的OMDVR产生分级血管舒张。这些结果表明，肾上腺素能和胆碱能神经支配可影响OMDVR的血管运动张力，以调节肾髓质的总血流量和局部血流量。数据还支持组成型表达的一氧化氮合酶的活性在调节OMDVR血管活性中起作用。
