Henley W N, Bellush L L, Tucker A
Department of Zoological and Biomedical Sciences, Ohio University, Athens 45701.
Proc Soc Exp Biol Med. 1989 Nov;192(2):114-20. doi: 10.3181/00379727-192-42964.
Exposure to hypobaric hypoxia (H; simulated altitude = 3658 m) was initiated in 5-week-old, male spontaneously hypertensive (SHR) and Wistar-Kyoto (WKy) normotensive rats while normoxic controls (N) for both groups were maintained under laboratory conditions. Significant attenuation of systolic arterial blood pressure was evident in SHR-H relative to SHR-N (125 +/- 6 vs 145 +/- 5 mm Hg; P less than 0.05) but not in WKy-H relative to WKy-N (WKy-H, 116 +/- 2 vs WKy-N, 117 +/- 5 mm Hg). Hypoxia significantly decreased metabolic efficiency in both normotensive and hypertensive rats, although being both more severe and accompanied by significantly impaired growth rate in SHR-H. Urinary excretion of norepinephrine in the SHR was elevated relative to WKy, irrespective of altitude treatment, while hypoxia elicited similar increases in urinary excretion of norepinephrine in both SHR and WKy. Myocardial and adrenal contents of norepinephrine were significantly reduced following 3 days of simulated altitude exposure in both strains of rats. Tissue contents of norepinephrine in hypoxic rats returned to normoxic levels by 21 days of simulated altitude. Both urine and tissue indices provided consistent indirect evidence that changes in sympathetic neuronal activity in response to hypoxia were similar in normotensive and hypertensive rats. These findings suggest that prior reports of reduced alpha-adrenergic responsiveness in vasculature from hypoxia-exposed SHR reflect a postsynaptic event that is regulated independently of norepinephrine release from sympathetic nerve terminals.
对5周龄的雄性自发性高血压（SHR）大鼠和Wistar-Kyoto（WKy）正常血压大鼠开始进行低压低氧暴露（H；模拟海拔 = 3658米），而两组的常氧对照组（N）维持在实验室条件下。与SHR-N相比，SHR-H的收缩期动脉血压明显降低（125±6 vs 145±5毫米汞柱；P<0.05），但与WKy-N相比，WKy-H没有降低（WKy-H，116±2 vs WKy-N，117±5毫米汞柱）。低氧显著降低了正常血压和高血压大鼠的代谢效率，尽管在SHR-H中更严重且伴有生长速率明显受损。无论海拔处理如何，SHR的去甲肾上腺素尿排泄量相对于WKy都有所升高，而低氧在SHR和WKy中均引起去甲肾上腺素尿排泄量类似的增加。在两种品系的大鼠中，模拟海拔暴露3天后，心肌和肾上腺中的去甲肾上腺素含量显著降低。到模拟海拔21天时，低氧大鼠的组织去甲肾上腺素含量恢复到常氧水平。尿液和组织指标均提供了一致的间接证据，表明正常血压和高血压大鼠对低氧反应时交感神经元活动的变化相似。这些发现表明，先前关于低氧暴露的SHR血管中α-肾上腺素能反应性降低的报道反映了一种突触后事件，该事件独立于交感神经末梢释放的去甲肾上腺素进行调节。
