Jain S, Wilke W L, Tucker A
Department of Physiology, Colorado State University, Fort Collins 80523.
J Appl Physiol (1985). 1990 Jul;69(1):141-6. doi: 10.1152/jappl.1990.69.1.141.
The mechanisms regulating water, electrolyte, and blood volume homeostasis continue to mature in early postnatal life, and this maturation may be altered by perturbations of volume or cardiovascular status. To evaluate the long-term effects of chronic hypoxia on water balance, urinary electrolyte excretion, heart weights, systemic arterial pressure, and components of the renin-angiotensin system, male Sprague-Dawley rats were exposed to periods of simulated altitude of 10,000 ft up to 90 days of age beginning at 2 or 30 days of age. Altitude exposure of both neonatal and adult rats was associated with increases in urine output and water intake after 30 days of exposure, and right ventricular (RV) hypertrophy at all ages was examined. However, the percent increase in urine output, water intake, and RV hypertrophy was numerically greater in neonates. Neonates also had increases in urinary sodium and potassium excretion after 30 days of exposure. Plasma renin activity and serum angiotensin-converting enzyme (ACE) activity were not affected, but plasma renin substrate was reduced in both neonatal and adult altitude-exposed rats. Lung ACE activity was also decreased in altitude-exposed neonates. These data indicate that the degree and, in some cases, the nature of these homeostatic responses varies with age during long-term hypoxia.
调节水、电解质和血容量稳态的机制在出生后早期仍在持续成熟，而这种成熟可能会因容量或心血管状态的扰动而改变。为了评估慢性缺氧对水平衡、尿电解质排泄、心脏重量、体循环动脉压以及肾素-血管紧张素系统各组分的长期影响，雄性斯普拉格-道利大鼠在2日龄或30日龄开始暴露于相当于海拔10,000英尺的模拟环境中，直至90日龄。新生大鼠和成年大鼠暴露于该海拔环境30天后，均出现尿量和饮水量增加，且对各年龄段的右心室（RV）肥大情况进行了检查。然而，新生儿的尿量、饮水量和RV肥大的增加百分比在数值上更大。暴露30天后，新生儿的尿钠和钾排泄量也增加。血浆肾素活性和血清血管紧张素转换酶（ACE）活性未受影响，但暴露于海拔环境的新生大鼠和成年大鼠的血浆肾素底物均减少。暴露于海拔环境的新生大鼠的肺ACE活性也降低。这些数据表明，在长期缺氧期间，这些稳态反应的程度以及在某些情况下其性质会随年龄而变化。
