Tabrizchi R
Division of Basic Medical Sciences, Faculty of Medicine, Memorial University of Newfoundland, St. John's, Canada.
Eur J Pharmacol. 1998 Nov 20;361(2-3):227-34. doi: 10.1016/s0014-2999(98)00714-6.
Hypovolemia has been associated with the induction of nitric oxide synthase which is believed to result in an over-production of nitric oxide. In the present study, we have examined the effects of noradrenaline following haemorrhage on cardiac output, blood pressure, mean circulatory filling pressure and vascular resistance in anaesthetized rats after pre-treatment with nitric oxide synthase inhibitor, L-N6-(1-iminoethyl)lysine or dexamethasone. Hypovolemic haemorrhage resulted in induction of nitric oxide synthase, as measured in lungs, and both dexamethasone and L-N6-(1-iminoethyl)lysine inhibited the activity of the inducible form of nitric oxide synthase. An infusion of noradrenaline significantly increased cardiac output, blood pressure and mean circulatory filling pressure in animals pre-treated with L-N6-(1-iminoethyl)lysine and dexamethasone when compared with saline pre-treatment. In addition, the administration of noradrenaline significantly reduced venous resistance in animals pre-treated with L-N6-(1-iminoethyl)lysine when compared with saline pre-treatment. The results of this investigation indicated that the impact of noradrenaline on cardiac output, blood pressure and mean circulatory filling pressure was greater in hypovolemic rats treated with L-N6-(1-iminoethyl)lysine or dexamethasone. In addition, we found that in the hypovolemic state, the greater increase in cardiac output during the infusion of noradrenaline after inhibition of nitric oxide synthase was predominantly due to reduced resistance to venous return.
低血容量已与一氧化氮合酶的诱导相关联，据信这会导致一氧化氮产生过量。在本研究中，我们在用一氧化氮合酶抑制剂L-N6-(1-亚氨基乙基)赖氨酸或地塞米松预处理后，研究了出血后去甲肾上腺素对麻醉大鼠的心输出量、血压、平均循环充盈压和血管阻力的影响。低血容量性出血导致肺中可测量到的一氧化氮合酶的诱导，而地塞米松和L-N6-(1-亚氨基乙基)赖氨酸均抑制诱导型一氧化氮合酶的活性。与生理盐水预处理相比，给用L-N6-(1-亚氨基乙基)赖氨酸和地塞米松预处理的动物输注去甲肾上腺素可显著增加心输出量、血压和平均循环充盈压。此外，与生理盐水预处理相比，给用L-N6-(1-亚氨基乙基)赖氨酸预处理的动物给予去甲肾上腺素可显著降低静脉阻力。本研究结果表明，在用L-N6-(1-亚氨基乙基)赖氨酸或地塞米松治疗的低血容量大鼠中，去甲肾上腺素对心输出量、血压和平均循环充盈压的影响更大。此外，我们发现，在低血容量状态下，一氧化氮合酶抑制后输注去甲肾上腺素期间心输出量的更大增加主要是由于对静脉回流的阻力降低。
