Factors affecting sodium reabsorption by the proximal tubule as determined during blockade of distal sodium reabsorption.

Earley, Laurence E.; Martino, Joseph A.; Friedler, Robert M.

doi:10.1172/jci105474

Cited by 133 publications

(95 citation statements)

References 28 publications

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“…In the absence of medullary autoregulation pressure will rise in those capillaries which originate from the juxtamedullary glomeruli and surround the short loops of Henle. As proposed by Earley et al (34,35) and Lewy and Windhager (36), such a change in the hydrostatic pressure gradient could result in a reduction of sodium and water reabsorption. Furthermore, as already mentioned, juxtamedullary filtration rate is strikingly elevated in chronic hypertension (30).…”

Section: Methodsmentioning

confidence: 91%

Fluid reabsorption in Henle's loop and urinary excretion of sodium and water in normal rats and rats with chronic hypertension

Stumpe¹,

Lowitz²,

Ochwadt³

1970

J. Clin. Invest.

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A B S T R A C T The function of the short loops of Henle was investigated by micropuncture technique in normal rats, in rats with spontaneous hypertension, and in the untouched kidney of rats with experimental renal hypertension. All animals received a standard infusion of 1.2 ml of isotonic saline per hr.With increasing arterial blood pressure (range from 90 to 220 mm Hg), a continuous decrease in transit time of Lissamine green through Henle's loop from 32 to 10 sec was observed. Fractional water reabsorption along the loop declined progressively from 26 to 10%, and fractional sodium reabsorption decreased from 40 to 36% of the filtered load. The fluid volume in Henle's loop calculated from transit time and mean flow rate also decreased with increasing blood pressure. There was no change in superficial single nephron filtration rate but there was a slight increase in total glomerular filtration rate (GFR). Sodium and water reabsorption in the proximal tubule remained unchanged.Urine flow rate, sodium excretion, osmolar clearance, and negative free water clearance increased with increasing blood pressure. The osmolal urine to plasma (U/P) ratio declined but did not fall below a value of 1.5. It is concluded that the increase in sodium and water excretion with chronic elevation of arterial blood pressure is caused by a decrease of sodium and water reabsorption along the loop of Henle, presumably as a consequence of increased medullary blood pressure. The following three groups of animals were used: (a) normal rats, (b) rats with a moderate spontaneous hypertension, and (c) rats with experimental hypertension 4-5 wk after clamping one renal artery with a Goldblatt clamp. In the last group, only the untouched kidney, which is exposed to the high blood pressure, was investigated. All animals received an isotonic saline infusion of 1.2 ml/hr. Micropuncture experiments were done on superficial nephrons. Accordingly, only the function of short loops of Henle was studied. METHODSThe experiments were performed on Albino rats of about the same weight (190-210 g). The animals were divided into three groups differing from each other by the level of arterial blood pressure. For the first group male rats-of the FW4, strain (Paderborn) were chosen, having a mean arterial blood pressure between 90 and 110 mm Hg. The second group consisted of female rats of the Wistar strain with a blood pressure from 110 to 160 mm Hg. In the third group female Wistar rats with experimental renal hypertension of 4-5 wk duration (for the method see reference 12, 13) were used, their blood pressure ranging from 160 to 220 mm Hg. In this last group only the untouched kidney exposed to the high arterial blood pressure was investigated. All animals were kept on the same standard rat diet (Altromin, sodium content: 1200 mg/kg) and had free access to water. The animals were anaesthetized by intraperitoneal injection of Inactin Hamburg,(70)(71)(72)(73)(74)(75)(76)(77)(78)(79)(80) mg/kg body weight) and prepared for micropuncture as previously describe...

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Section: Methodsmentioning

confidence: 91%

Fluid reabsorption in Henle's loop and urinary excretion of sodium and water in normal rats and rats with chronic hypertension

Stumpe¹,

Lowitz²,

Ochwadt³

1970

J. Clin. Invest.

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“…First, it is possible that an adjustment in renal hemodynamics may occur in the reduced kidney, leading to the relative increase in the perfusion of each nephron and this may result in changes in physical factors within the peritubular capillaries of the superficial proximal tubule in favor of reduction of fractional reabsorption (23,24). However, such a hemodynamic alteration within the cortex of stage III remnant kidney has not been convincingly demonstrated.…”

Section: Discussionmentioning

confidence: 99%

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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“…In the new-born dog, acute changes in filtered sodium loads result in proportional changes in proximal tubular sodium reabsorption, demonstrating good glomerulo-tubular balance (Kleinman, 1975). In new-born dogs expansion of the extracellular space with isotonic saline infusion produces a 20% reduction in proximal fractional sodium reabsorption (Kleinman, 1975), a value similar to that for the adult (Earley, Martino & Friedler, 1966). In sharp contrast, however, the new-born dog excretes only 1-2 % of the total filtered sodium during saline expansion whereas the adult excretes 6-7 % under the same conditions (Kleinman, 1975;Kleinman & Reuter, 1974), suggesting that segments of the nephron distal to the proximal tubule must be reabsorbing more sodium in the new-born than in the adult animal.…”

Section: Introductionmentioning

confidence: 89%

Effect of amiloride on the renal response to saline expansion in new‐born dogs.

Banks¹,

Kleinman²

1978

The Journal of Physiology

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SUMMARY1. The renal effects of amiloride were studied in twenty-six new-born and nine adult dogs, with and without saline expansion.2. Without saline expansion, amiloride inhibited more sodium reabsorption (normalized to GFR) in puppies than in adults (5.95 vs. 2-18 ,tequiv/ml. GFR, P < 0.01).Amiloride inhibited sodium reabsorption more in saline expanded than in nonexpanded puppies (9.39 vs. 5.95 #sequiv/ml. GFR, P < 0.01) but there was no difference between expanded and non-expanded adults.3. Saline expansion by itself increased fractional sodium excretion (CNa/GFR) more in the adult than in the puppy (0-071 vs. 0-019, P < 0-01). During amiloride inhibition, saline expansion increased CNa/GFR to 0*045 in the puppy (compared to 0X019 in the nonamiloride inhibited puppy) but saline expansion increased CNa/GFR to the same degree in the amiloride as in the non-amiloride inhibited adult. 4. In all puppies amiloride inhibited more sodium reabsorption than potassium secretion and there was poor correlation between the degree of inhibition of sodium reabsorption and potassium secretion for both the puppy (r = 0.14) and the adult (r = 0.05).5. Assuming that amiloride acts by inhibiting sodium reabsorption and potassium secretion in the late distal and cortical collecting tubules, these results support the conclusion that in these regions of the nephron of the new-born dog (a) a greater fraction of the filtered sodium is reabsorbed than in the adult and (b) increased fractional sodium reabsorption is responsible, in part, for the attenuated natriuretic response to saline expansion.

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Factors affecting sodium reabsorption by the proximal tubule as determined during blockade of distal sodium reabsorption.

Cited by 133 publications

References 28 publications

Fluid reabsorption in Henle's loop and urinary excretion of sodium and water in normal rats and rats with chronic hypertension

Fluid reabsorption in Henle's loop and urinary excretion of sodium and water in normal rats and rats with chronic hypertension

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

Effect of amiloride on the renal response to saline expansion in new‐born dogs.

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