Mechanism by which dietary protein enhances renal concentrating ability

Manitius, A; Pigeon, G; Epstein, Franklin H.

doi:10.1152/ajplegacy.1963.205.1.101

Cited by 23 publications

(9 citation statements)

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“…The increase can wholly be accounted for by the increased urea concentration. Non-urea solute concentration was similar before and after vasopressin (346 and 339 mmoljl), as previously reported in man (Edelmann et al, 1966;Steinmetz & Smith, 1963), but not in animals (Bray & Preston, 1961;Manitius, Pigeon & Epstein, 1963) receiving urea supplementation.…”

Section: Effect Of Urea On a Cirrhotic Patientsupporting

confidence: 87%

“…In man and animals receiving a low protein diet the maximal urine osmolality and T~zo are diminished (Epstein, Kleeman, Pursel & Hendrikx, 1957;Jaenike, 1963;Levinsky & Berliner, 1959;Manitius et 01., 1963) and a decreased renal medullary tissue urea concentration has been found in animal experiments (Levinsky & Berliner, 1959;Manitius et al, 1963). Before vasopressin administration the cirrhotic patients had a higher overall fractional tubular reabsorption of urea than controls.…”

Section: Discussionmentioning

confidence: 84%

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The Role of Vasopressin and Urea in the Renal Concentrating Defect of Patients with Cirrhosis of the Liver

Vaamonde

Presser

et al. 1971

Clinical Science

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1. The maximal urine osmolality in response to vasopressin during water diuresis and during hydropenia was studied in twenty patients with cirrhosis and sixteen noncirrhotic subjects under controlled dietary conditions.2. The cirrhotic patients exhibited a significantly lower maximal urine osmolality under both experimental conditions.3. During water diuresis decompensated and compensated cirrhotics had comparable maximal urine osmolalities after vasopressin. A decreased response of the renal tubules to vasopressin does not appear to have a significant role in the concentrating defect.4. The cirrhotic patients had a significantly lower excretion rate of urea at high (water diuresis) and low (vasopressin antidiuresis or hydropenia) urine flow rates. The lower urine urea concentration accounted for most of the decrease observed in maximal urinary concentration. After vasopressin administration the absolute tubular reabsorption of urea was also significantly lower in cirrhotic patients. The results suggest that a decrease in the medullary urea content decreases medullary osmolality resulting in the defect in urine concentration noted in these cirrhotic patients at low urine flow rates. 5. Protein depletion or decreased urea synthesis may in part be responsible for the decreased availability of urea for the concentrating process in cirrhosis.6. Lack of correlation between concentrating and diluting capacity in these patients suggested that decreased delivery of sodium to the distal site might not be the limiting factor common to both renal functional abnormalities observed in cirrhosis of the liver.Previous studies from our laboratory have described a reversible renal concentrating defect in patients with cirrhosis of the liver characterized by decreased maximal urinary solute concentra-

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Section: Effect Of Urea On a Cirrhotic Patientsupporting

confidence: 87%

Section: Discussionmentioning

confidence: 84%

The Role of Vasopressin and Urea in the Renal Concentrating Defect of Patients with Cirrhosis of the Liver

Vaamonde

Presser

et al. 1971

Clinical Science

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“…For 1 week before the experiment, 27 animals were maintained on a standard diet containing more than 100 g protein per day and adequate minerals and vitamins. In three a synthetic nonprotein diet similar to that utilized by Manitius, Pigeon, and Epstein (14) was substituted for the standard diet. On the day before each experiment, water was withheld, and 5 U of Pitressin tannate in oil was administered.…”

Section: Methodsmentioning

confidence: 99%

“…Whether urea reaches the medullary interstitium by active transport, as suggested by our data, or by passive mechanisms, it would accumulate in the inner medulla according to the principles of countercurrent exchange involving the vasa recta (3) and increase papillary and urinary osmolality. An active transport system could, in addition, account for the increase in urinary nonurea solute concentration observed under certain conditions after administration of urea and protein (11,14).…”

Section: Methodsmentioning

confidence: 99%

Uphill Transport of Urea in the Dog Kidney: Effects of Certain Inhibitors*

Goldberg¹,

Wojtczak²,

Ramirez³

1967

J. Clin. Invest.

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Summary. To study the renal medullary transport and accumulation of urea in dogs independent of water transport, we obliterated the medullary electrolyte gradient by a sustained ethacrynic acid diuresis. Infusions of urea were also given at various rates to vary urinary urea concentration. In the steady state, the kidneys were removed, and slices were analyzed for water, urea, and electrolytes. In every experiment in 15 dogs over a range of urinary urea concentration from 19 to 230 mmoles per L and urine flow from 0.5 to 9.7 ml per minute per kidney, an intrarenal urea gradient persisted, and urinary urea concentration was always lower than papillary water urea concentration. The magnitude of this uphill urinary-papillary gradient (mean + SE = -21 + 2.9 mmoles per L) was not affected by hemorrhagic hypotension or a nonprotein diet.In 12 additional experiments begun similarly, inhibitors were infused into one renal artery. Both iodoacetate, an inhibitor of anaerobic glycolysis, and acetamide, an analogue of urea, markedly and significantly reduced both the intrarenal urea gradient and the uphill urinary-papillary gradient. In contrast, cyanide, an inhibitor of oxidative metabolism, had no observable effect on the urea gradients. The data are best explained by postulating an active transport system for urea in the medullary collecting duct deriving its energy from anaerobic glycolysis.

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“…Our interpretation of this cycle is shown in Figure 7. During antidiuresis water reabsorption from the lower nephron increases (26). Substantiation of this hypothesis must await further experimental observations.…”

Section: Discussionmentioning

confidence: 95%