Renal response to graded saline challenge

Bb, Davis; Mj, Walter; Hv, Murdaugh

doi:10.1152/ajplegacy.1969.217.6.1604

Cited by 11 publications

(6 citation statements)

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“…The demonstration by Davis, Walters, and Murdaugh (27) in the dog that the magnitude of reduction in proximal tubule reabsorption remained constant at various levels of ECV expansion is consistent with our findings. On the other hand, micropuncture study in the rat by Brenner and Berliner (28) showed progressive response in proximal tubule reabsorption to graded ECV expansion.…”

Section: Discussionsupporting

confidence: 93%

Micropuncture Studies of Sodium Tranport in the Remnant Kidney of the Dog THE EFFECT OF GRADED VOLUME EXPANSION

Wen¹,

Wong²,

Evanson³

et al. 1973

J. Clin. Invest.

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A B S T R A C T Proximal and distal tubule micropuncture studies were performed to examine the response to graded extracellular volume (ECV) expansion in 10 normal dogs (stage I), 11 dogs with a unilateral remnant kidney (stage II), and 7 dogs with a remnant kidney after removal of the contralateral kidney (stage III). Before ECV expansion in stage III, there was a suggestive reduction in proximal tubule as well as loop fractional reabsorption of sodium. After ECV expansion to 3% body weight proximal tubule reabsorption was depressed in all groups of animals, while little further inhibition was observed in this segment with additional expansion to 10% body weight. In contrast, the fraction of filtered sodium remaining in the distal tubule rose progressively in all three groups after graded ECV expansion, suggesting that the graded natriuretic response found in the final urine was largely due to a similar response in the loop of Henle rather than that in the proximal tubule. The distal tubule response of the remnant kidney in both stages II and III was greater than that in stage I. These data indicate that although enhanced sodium excretion per nephron in chronic renal failure may be related to uremia, its exaggerated response to ECV expansion is due, at least in part, to cer-

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Section: Discussionsupporting

confidence: 93%

Micropuncture Studies of Sodium Tranport in the Remnant Kidney of the Dog THE EFFECT OF GRADED VOLUME EXPANSION

Wen¹,

Wong²,

Evanson³

et al. 1973

J. Clin. Invest.

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“…When subjects were divided into excreters and nonexcreters according to their maximum rates of Na excretion (Table IV), there was no significant further proximal inhibition in either group, when the saline load was increased from 6 to 8% body wt. The conclusion that inhibition of proximal FSR in man is relatively stable after moderate ECF expansion has been achieved is in agreement with several clearance and micropuncture studies in dogs and rats (7,8),2 although the contrary conclusion has been reached from micropuncture experiments in rats (6). No other observations in man have been published.…”

Section: Resultssupporting

confidence: 87%

“…Micropuncture experiments have demonstrated convincingly that the proximal tubule is one site at which fractional sodium reabsorption (FSR)' is inhibited by saline loading (5). The evidence is conflicting as to whether the magnitude of proximal inhibition is correlated with the volume of saline infused (6)(7)(8)(9). One study (10) suggested that chronic extracellular expansion also inhibits proximal FSR but subsequently (11) proximal FSR was found to be unchanged.…”

Section: Introductionmentioning

confidence: 99%

Tubular reabsorption of sodium during acute and chronic volume expansion in man

Alexander¹,

Doner²,

Auld³

et al. 1972

J. Clin. Invest.

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A B S T R A C T Renal hemodynamics and tubular fractional sodium reabsorption (FSR) were evaluated by clearance techniques during acute and chronic extracellular volume expansion in man.(1 -V/GFR) X 100 was used as an index of proximal and (CH20/V) X 100 as an estimate of distal fractional reabsorption. After acute loading with isotonic saline 37 mVkg body wt, proximal FSR decreased by 4.8% and distal FSR decreased by 4.4%. After comparable chronic expansion by mineralocorticoids ("escape"), proximal FSR also decreased by 3.9%, but distal reabsorption was not altered.In separate studies, subjects were progressively infused with saline to 57 (Ei) and to 80 (E2) ml/kg body wt, and appeared to divide into "excreters" (maximum UNaV > 1000 /AEq/min) and "nonexcreters" (maximum UNaV < 550 iAEq/min). In the excreters, GFR rose, proximal FSR decreased by 7.1% after E1 and only 0.9% further after E2. Distal FSR fell by 14.8% after E1 and by an additional 4.9% after Es. In the nonexcreters, GFR was stable and proximal FSR did not fall significantly after E1 or E2. Distal FSR decreased 4.5% after El and 1.3% further after E2. It is concluded that both acute and chronic extracellular expansion decrease proximal FSR in man, but only acute loading depresses distal FSR. Ability of some men to excrete sodium rapidly after acute infusion is related to larger increases in GFR and greater decreases in both proximal and distal FSR than occur in men in whom natriuresis is more limited.

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“…To explain the observation that bicarbonate reabsorption remains elevated after daily sodium balance becomes neutral, we propose that proximal tubular reabsorption remains increased but that sodium balance is reestablished by a greater rejection of sodium at distal tubular sites. This proposal is in accord with evidence from both micropuncture and balance studies which suggest that proximal and distal tubular sodium reabsorption may be dissociated according to the needs of the organism (21)(22)(23)(24).…”

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confidence: 83%