Fletcher E C, Bao G
Department of Medicine, Louisville Veterans Affairs Medical Center, Kentucky, USA.
J Appl Physiol (1985). 1996 Nov;81(5):2088-94. doi: 10.1152/jappl.1996.81.5.2088.
Repetitive episodic (18-24 s twice per minute) hypocapnic hypoxia (HH) administered chronically (7 h/day, 35 days) to Sprague-Dawley or Wistar-Kyoto rats results in a sustained increase in daytime blood pressure (BP). We examined acute and chronic BP response to episodic HH and eucapnic hypoxia (EH) in borderline hypertensive rats [first generation (F1) cross between spontaneously hypertensive and Wistar-Kyoto rats]. We hypothesized that episodic HH and EH would create a greater increase in acute and chronic BP in this breed of rat than in previously studied strains. We also examined neural mechanisms by which BP changes from hypoxia are induced. BP and heart rate were examined acutely in nine F1 rats during baseline, HH, EH, EH with prazosin, and EH with prazosin and atropine. Five groups of male F1 rats were studied after 35-day exposure to the following: Unhandled (n = 8): no treatment; Sham (n = 10): episodic compressed air; HH (n = 14): daily episodic hypoxia (2.7%); EH1 (n = 12); hypoxia 2.9%, CO2 8.4%; and EH2 (n = 11): hypoxia 2.8% and CO2 10.5%. Under acute conditions, HH caused a 34.2-mmHg and EH a 77.9-mmHg increase in mean BP. Prazosin partially blocked the increase in BP. Under chronic conditions, HH caused a 10.3-mmHg increase in daytime mean BP, whereas EH caused a fall in mean BP of 16.6 and 9.3 mmHg in the two separately studied groups. In the F1 rat, acute EH causes an elevation of BP but chronic EH causes a fall in BP. The acute response to EH is not predictive of what occurs after chronic exposure in the hypertension-prone F-1 rat.
对Sprague-Dawley或Wistar-Kyoto大鼠长期（每天7小时，共35天）给予重复性发作性（每分钟两次，每次18 - 24秒）低碳酸血症性低氧（HH）会导致白天血压（BP）持续升高。我们研究了临界高血压大鼠[自发性高血压大鼠与Wistar-Kyoto大鼠的第一代（F1）杂交后代]对发作性HH和等碳酸血症性低氧（EH）的急性和慢性血压反应。我们假设，与先前研究的品系相比，发作性HH和EH会使该品系大鼠的急性和慢性血压升高幅度更大。我们还研究了低氧诱导血压变化的神经机制。在9只F1大鼠的基线、HH、EH、用哌唑嗪的EH以及用哌唑嗪和阿托品的EH期间急性检测血压和心率。五组雄性F1大鼠在暴露于以下情况35天后进行研究：未处理（n = 8）：未治疗；假手术（n = 10）：发作性压缩空气；HH（n = 14）：每日发作性低氧（2.7%）；EH1（n = 12）：低氧2.9%，二氧化碳8.4%；以及EH2（n = 11）：低氧2.8%，二氧化碳10.5%。在急性条件下，HH使平均血压升高34.2 mmHg，EH使平均血压升高77.9 mmHg。哌唑嗪部分阻断了血压升高。在慢性条件下，HH使白天平均血压升高10.3 mmHg，而在两个单独研究的组中，EH使平均血压分别下降16.6和9.3 mmHg。在F1大鼠中，急性EH导致血压升高，但慢性EH导致血压下降。对EH的急性反应并不能预测易患高血压的F1大鼠慢性暴露后的情况。
