Manohar M, Goetz T E, Hassan A S
Department of Veterinary Biosciences and Clinical Medicine, College of Veterinary Medicine, University of Illinois at Urbana-Champaign, Urbana, Illinois 61801, USA.
Equine Vet J Suppl. 2006 Aug(36):481-6. doi: 10.1111/j.2042-3306.2006.tb05591.x.
Work is required to establish the role of endogenous nitric oxide (NO) in metabolism of resting and exercising horses.
To examine the effects of NO synthase inhibition on O2 extraction and anaerobic metabolism at rest, and during submaximal and maximal exertion.
Placebo and NO synthase inhibition (with Nomega-nitro-L-arginine methyl ester [L-NAME] administered at 20 mg/kg bwt i.v.) studies were performed in random order, 7 days apart on 7 healthy, exercise-trained Thoroughbred horses at rest and during incremental exercise leading to 120 sec of maximal exertion at 14 m/sec on a 3.5% uphill grade.
At rest, NO synthase inhibition significantly augmented the arterial to mixed-venous blood O2 content gradient and O2 extraction as mixed-venous blood O2 tension and saturation decreased significantly. While NO synthase inhibition did not affect arterial blood-gas tensions in exercising horses, the exercise-induced increment in haemoglobin concentration and arterial O2 content was attenuated. In the L-NAME study, during submaximal exercise, mixed-venous blood O2 tension and haemoglobin-O2 saturation decreased to a greater extent causing O2 extraction to increase significantly. During maximal exertion, arterial hypoxaemia, desaturation of haemoglobin and hypercapnia of a similar magnitude developed in both treatments. Also, the changes in mixed-venous blood O2 tension and haemoglobin-O2 saturation, arterial to mixed-venous blood O2 content gradient, O2 extraction and markers of anaerobic metabolism (lactate and ammonia production, and metabolic acidosis) were not different from those in the placebo study.
Endogenous NO production augments O2 extraction at rest and during submaximal exertion, but not the during short-term maximal exercise. Also, NO synthase inhibition does not affect anaerobic metabolism at rest or during exertion.
It is unlikely that endogenous NO release modifies aerobic or anaerobic metabolism in horses performing short-term maximal exertion.
需要开展工作以确定内源性一氧化氮（NO）在静息和运动马匹代谢中的作用。
研究一氧化氮合酶抑制对静息状态、次最大运动和最大运动时氧气摄取及无氧代谢的影响。
对7匹健康、经过运动训练的纯种马进行安慰剂和一氧化氮合酶抑制（静脉注射20mg/kg体重的Nω-硝基-L-精氨酸甲酯[L-NAME]）研究，研究随机顺序进行，间隔7天，分别在静息状态以及在3.5%上坡坡度以14米/秒速度进行递增运动直至120秒最大运动时进行。
静息状态下，一氧化氮合酶抑制显著增大了动脉血与混合静脉血氧含量梯度以及氧气摄取，因为混合静脉血氧分压和血氧饱和度显著降低。虽然一氧化氮合酶抑制对运动马匹的动脉血气张力无影响，但运动诱导的血红蛋白浓度和动脉血氧含量的增加减弱。在L-NAME研究中，次最大运动期间，混合静脉血氧分压和血红蛋白氧饱和度下降幅度更大，导致氧气摄取显著增加。最大运动期间，两种处理均出现了相似程度的动脉低氧血症、血红蛋白去饱和和高碳酸血症。此外，混合静脉血氧分压和血红蛋白氧饱和度的变化、动脉血与混合静脉血氧含量梯度、氧气摄取以及无氧代谢标志物（乳酸和氨生成以及代谢性酸中毒）与安慰剂研究中的情况无差异。
内源性NO生成在静息和次最大运动时增强氧气摄取，但在短期最大运动时则不然。此外，一氧化氮合酶抑制在静息或运动时不影响无氧代谢。
内源性NO释放不太可能改变进行短期最大运动马匹的有氧或无氧代谢。
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