Massett M P, Lewis S J, Bates J N, Kregel K C
Department of Exercise Science, The University of Iowa, Iowa City, Iowa 52242, USA.
J Appl Physiol (1985). 1998 Aug;85(2):701-8. doi: 10.1152/jappl.1998.85.2.701.
Vasoconstriction in the viscera is one of the primary cardiovascular adjustments to heating. Local temperature can influence vascular responsiveness to catecholamines and sympathetic nerve activity. Therefore, we hypothesized that heating would alter vascular reactivity in rat mesenteric arteries. Concentration-response curves to norepinephrine, phenylephrine, potassium chloride (KCl), calcium, acetylcholine, and sodium nitroprusside were obtained in vascular ring segments from rat mesenteric arteries at 37 and 41 degrees C. In some rings, basal tension increased slightly during heating. Heating to 41 degrees C did not alter the contractile responses to norepinephrine in endothelium-intact or -denuded rings but augmented the responses to KCl and calcium in endothelium-intact rings. The potentiating effect of heating on the responses to KCl and calcium was eliminated after endothelium removal. In contrast, the relaxant responses to acetylcholine and sodium nitroprusside were significantly attenuated at 41 degrees C. Collectively, these results demonstrate that heating alters vascular reactivity in rat mesenteric arteries. Furthermore, these data imply that heating reduces the ability of vascular smooth muscle to relax, possibly due to a decrease in sensitivity to nitric oxide.
内脏血管收缩是对受热的主要心血管适应性反应之一。局部温度可影响血管对儿茶酚胺的反应性以及交感神经活动。因此，我们推测受热会改变大鼠肠系膜动脉的血管反应性。在37℃和41℃条件下，从大鼠肠系膜动脉获取血管环段，得到去甲肾上腺素、苯肾上腺素、氯化钾（KCl）、钙、乙酰胆碱和硝普钠的浓度-反应曲线。在一些血管环中，受热期间基础张力略有增加。加热至41℃不会改变内皮完整或去内皮血管环对去甲肾上腺素的收缩反应，但会增强内皮完整血管环对KCl和钙的反应。去除内皮后，受热对KCl和钙反应的增强作用消失。相反，在41℃时，对乙酰胆碱和硝普钠的舒张反应显著减弱。总体而言，这些结果表明受热会改变大鼠肠系膜动脉的血管反应性。此外，这些数据表明受热可能由于对一氧化氮敏感性降低而降低了血管平滑肌的舒张能力。
