Sagawa Sueko, Yamauchi Katsuya, Tsutsui Yuka, Endo Yutaka, Shiraki Keizo
Department of Sports Life Style Management, National Institute of Fitness and Sports, Kanoya, Japan.
Aviat Space Environ Med. 2005 Aug;76(8):739-43.
Accumulated evidence indicates attenuated vasopressin (AVP) release associated with hyperbaria in humans. The present study was designed to test the hypothesis that plasma AVP response to central hypovolemia was attenuated in a hyperbaric environment.
Response of AVP to central hypovolemic stress, in the form of lower-body negative pressure (LBNP), was measured in 10 men at 1 and 3 atmosphere absolute (ATA) air. The stress consisted of 4 min each of control and LBNP at -20 and -40 mmHg. Plasma AVP, plasma norepinephrine (NE), plasma osmolality, and hematocrit (Hct) were measured. Thoracic impedance (Z0), and leg volume were also determined.
The baseline AVP (0.9 +/- 0.3 pg x ml(-1)) at 1 ATA increased significantly in response to -40 mmHg LBNP (1.8 +/- 0.6 pg x ml(-1)), but the increase was attenuated at 3 ATA (1.2 +/- 0.8 pg x ml(-1)). The baseline NE at 3 ATA was lower by 22.4 pg x ml(-1) than that of 1 ATA (226.5 pg x ml(-1)). NE increased with increasing LBNP at both environmental pressures, but the increase was independent of the pressure. Changes in Z0, reflecting thoracic blood volume, were identical in both environments. Mean arterial pressure, plasma osmolality, and Hct remained constant throughout the experimental period. Leg volume increased stress dependently during LBNP (approximately 34 ml at -20 mmHg; approximately 74 ml at -40 mmHg) and the increment was similar in the two environments.
The present study revealed that hyperbaria attenuated the response of AVP and NE to hypovolemic stress. The attenuated AVP response to LBNP was associated with neither plasma osmolality nor intrathoracic blood shift.
越来越多的证据表明，人类在高压环境下血管加压素（AVP）释放减弱。本研究旨在验证以下假设：在高压环境中，血浆AVP对中枢性低血容量的反应会减弱。
在10名男性中，于1个绝对大气压（ATA）和3个ATA的空气环境下，测量AVP对以下体负压（LBNP）形式出现的中枢性低血容量应激的反应。应激包括在-20和-40 mmHg下各4分钟的对照期和LBNP期。测量血浆AVP、血浆去甲肾上腺素（NE）、血浆渗透压和血细胞比容（Hct）。还测定了胸部阻抗（Z0）和腿部容积。
在1个ATA时，基线AVP（0.9±0.3 pg/ml）在-40 mmHg LBNP作用下显著增加（1.8±0.6 pg/ml），但在3个ATA时增加减弱（1.2±0.8 pg/ml）。3个ATA时的基线NE比1个ATA时低22.4 pg/ml（1个ATA时为226.5 pg/ml）。在两种环境压力下，NE均随LBNP增加而升高，但升高与压力无关。反映胸部血容量的Z0变化在两种环境中相同。在整个实验期间，平均动脉压、血浆渗透压和Hct保持恒定。在LBNP期间，腿部容积随应激增加（-20 mmHg时约增加34 ml；-40 mmHg时约增加74 ml），且在两种环境中的增加相似。
本研究表明，高压减弱了AVP和NE对低血容量应激的反应。AVP对LBNP的反应减弱既与血浆渗透压无关，也与胸腔内血液转移无关。
