Keeler R, Azzarolo A M
Department of Physiology, Faculty of Medicine, University of British Columbia, Vancouver, Canada.
Am J Physiol. 1991 Jun;260(6 Pt 2):R1183-7. doi: 10.1152/ajpregu.1991.260.6.R1183.
Renal excretory patterns for inulin and 22Na were measured in rats after simultaneous injection into a renal artery. In normal rats, the excretion of 22Na was much faster than inulin. This is referred to as "precession of sodium" and showed that some of the excreted 22Na had bypassed the intratubular route. During water diuresis, 65% of excreted 22Na was excreted before inulin. The quantity of 22Na preceding inulin (0.10 +/- 0.03% of the amount injected) increased eightfold during infusion of atrial natriuretic peptide (ANP). In saline diuresis, 45% of excreted 22Na (1.47 +/- 0.39% of the amount injected) preceded inulin, but precession was not affected by ANP. In rats with a nephrotic syndrome, 13% of excreted 22Na (0.34 +/- 0.12% of the amount injected) preceded inulin during saline diuresis and increased to 1.66 +/- 0.53% of the amount injected during the infusion of ANP. Precession of sodium was completely abolished in kidneys with papillary necrosis, suggesting that 22Na entered the tubular lumen in the inner medulla. These experiments demonstrate that, in rats, a large fraction of excreted sodium enters the tubules by a route other than filtration. The quantity of sodium entering the tubules by this route shows a 10- to 15-fold variation under conditions that modify the rate of sodium excretion.
在大鼠肾动脉同时注射菊粉和22钠后，测量了它们的肾脏排泄模式。在正常大鼠中，22钠的排泄比菊粉快得多。这被称为“钠的先排”，表明一些排泄的22钠绕过了肾小管途径。在水利尿期间，65%的排泄22钠在菊粉之前排出。在心房利钠肽（ANP）输注期间，先于菊粉的22钠量（注射量的0.10±0.03%）增加了八倍。在盐利尿期间，45%的排泄22钠（注射量的1.47±0.39%）先于菊粉排出，但先排不受ANP影响。在患有肾病综合征的大鼠中，在盐利尿期间，13%的排泄22钠（注射量的0.34±0.12%）先于菊粉排出，在输注ANP期间增加到注射量的1.66±0.53%。在患有乳头坏死的肾脏中，钠的先排完全消失，这表明22钠进入了内髓质的肾小管腔。这些实验表明，在大鼠中，很大一部分排泄的钠通过滤过以外的途径进入肾小管。在改变钠排泄率的条件下，通过该途径进入肾小管的钠量显示出10至15倍的变化。
