Greenberg S G, Enders C, Osborn J L
Department of Physiology, Medical College of Wisconsin, Milwaukee 53226.
Hypertension. 1993 Jul;22(1):1-8. doi: 10.1161/01.hyp.22.1.1.
The spontaneously hypertensive rat (SHR) has an elevated efferent sympathetic nerve activity, suggesting that the renal handling of sodium and water may be altered. This study evaluated the renal neurogenic influence on the rate of achieving sodium balance in adult SHRs and Wistar-Kyoto (WKY) rats after either a step increase or step decrease in fixed sodium intake. Conscious, unrestrained rats with either innervated or denervated kidneys were initially placed on a low-sodium (0.3 mEq/d) or high-sodium (5.0 mEq/d) intake by intravenous infusion. Hourly urinary sodium excretion was determined 24 hours before and 72 hours after sodium intake had been increased from low to high or decreased from high to low. After either step change in fixed sodium intake, both innervated SHRs and innervated WKY rats achieved sodium balance within 24 hours. Similarly, the time course of achieving sodium balance was nearly identical between WKY rats with innervated and denervated kidneys after either switch in sodium intake. In SHRs receiving a step increase in sodium intake, both innervated and denervated kidneys increased urinary sodium excretion equally for 9 hours; however, at this time, innervated SHRs continued to increase sodium excretion rapidly, whereas denervated rats were delayed in a further response. Thus, innervated SHRs achieved sodium balance approximately 18 hours sooner than denervated SHRs. Differences in urinary sodium excretion did not result from concomitant changes in plasma renin activity or mean arterial pressure.(ABSTRACT TRUNCATED AT 250 WORDS)
自发性高血压大鼠(SHR)的传出交感神经活动增强,这表明其肾脏对钠和水的处理可能发生了改变。本研究评估了成年SHR和Wistar-Kyoto(WKY)大鼠在固定钠摄入量阶梯式增加或减少后,肾脏神经源性因素对实现钠平衡速率的影响。将有意识、未受束缚且肾脏有神经支配或去神经支配的大鼠,最初通过静脉输注给予低钠(0.3 mEq/d)或高钠(5.0 mEq/d)摄入。在钠摄入量从低增加到高或从高降低到低之前24小时和之后72小时,每小时测定尿钠排泄量。在固定钠摄入量发生任何一种阶梯式变化后,有神经支配的SHR和有神经支配的WKY大鼠均在24小时内实现了钠平衡。同样,在钠摄入量发生任何一种变化后,有神经支配和去神经支配的WKY大鼠实现钠平衡的时间进程几乎相同。在钠摄入量阶梯式增加的SHR中,有神经支配和去神经支配的肾脏在9小时内尿钠排泄量均同等增加;然而,此时,有神经支配的SHR继续迅速增加钠排泄,而去神经支配的大鼠进一步反应延迟。因此,有神经支配的SHR比去神经支配的SHR早约18小时实现钠平衡。尿钠排泄的差异并非由血浆肾素活性或平均动脉压的伴随变化所致。(摘要截短至250字)