脑室内注射高张盐水抑制近曲小管对水和钠的重吸收

INTRACEREBROVENTRICULAR ADMLNISTRATION OF HYPERTONIC SALINE INHIBITS THE REABSORPTION OF WATER AND SODIUM IN THE PROXIMAL TUBULE

实验在麻醉大鼠上进行。用锂清除率为指标观察脑室内注射高张盐水对近曲小管重吸收水和钠的影响。在切断单侧肾神经的动物中,脑室内注射高张盐水后的锂清除率与肾小球滤过率比值在去神经侧肾脏从0.37±0.04增加至0.51±0.05(P<0.01);神经完好侧肾脏则从0.26±0.03增加至0.31±0.04(P<0.05);双侧肾脏的肾小球滤过率、尿量、尿钠和尿钾量均增加,且去肾神经肾脏的增加幅度高于肾神经完好肾脏。在肾小管微穿刺实验中,脑室内注射高张盐水后,近曲小管末段小管液流量从24.42±1.84nl/min增加至31.86±3.09nl/min(P<0.01),小管液的渗透压无显著变化。以上实验结果表明,脑室内注射高张盐水引起的利尿、尿钠增多反应与肾小球滤过率增加和近曲小管对水、钠重吸收减少有关,体液因素在该反应中可能起主要作用。

In anaesthetized rats with unilateral section of the renal nerve, the effect of intracerebroventricular (icv.) administration of hypertonic saline on the reabsorption of water and sodium in the proximal tubule was investigated, using the lithium clearance method.After icv. administration of hypertonic saline, the lithium clearance (C_(Li) to glomerular filtration rate (GFR) ratio increased from 0.37±0.04 to 0.51±0.05 (P<0.01) in the denervated kidneys and from 0.26±0.03 to 0.31±0.04 (P<0.05) in the innervated kidneys, respectively. GFR, urine flow rate (V), urinary sodium excretion (U_(Na)V)and urinary potassium excretion (U_kV)increased in both innervated and denervated kidneys, the increments of V, U_(Na)V and U_kV being greater in the denervated kidneys than in the innervated kidneys. In micropuncture experiments, icv. administration of hypertonic saline caused an increase in proximal tubule flow rate, from 24.42±1.84 nl/min to 31.86±3.09 nl/min, without significant change in proximal tubule fluid osmolality in the innervated kidneys. These data support the notion that the diuresis and natriuresis induced by icv. administration of hypertonic saline in the anaesthetized rat result from an increase in GFR and a decrease in the reabsorption of water and sodium in the proximal tubule. Humoral factors are probably involved in these responses.