Urea concentrations in tubular fluid and in renal tissue of nondiuretic rats

Roch-Ramel, F; Chométy, Françoise; Peters, G.

doi:10.1152/ajplegacy.1968.215.2.429

Cited by 37 publications

(16 citation statements)

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“…5) and Pu = 39 X 1O-' cm/s (Table I, IMCDA), and 6C = 70 mM, the calculated rate of urea absorption from the inner medullary collecting ducts is 1.4 X 10-3 mmol/min. If this value is compared with the filtered load of urea in normal rats (6 X 10-3 mmol/min [38]), the predicted urea absorption from the inner medullary collecting ducts will be 1.4/6 X 100% = 23% of the filtered load. This value is consistent with the range observed (15-30%) in micropuncture and microcatherization studies (12 1 3), in-ofurea out ofthe pelvic space.…”

Section: Resultsmentioning

confidence: 99%

Urea permeability of mammalian inner medullary collecting duct system and papillary surface epithelium.

Sands¹,

Knepper²

1987

J. Clin. Invest.

154

123

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To compare passive urea transport across the inner medullary collecting ducts (IMCDs) and the papillary surface epithelium (PSE) of the kidney, two determinants of passive transport were measured, namely permeability coefficient and surface area. Urea permeability was measured in isolated perfused IMCDs dissected from carefully localized sites along the inner medullas of rats and rabbits. Mean permeability coefficients (X10-5 cm/s) in rat

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Section: Resultsmentioning

confidence: 99%

Urea permeability of mammalian inner medullary collecting duct system and papillary surface epithelium.

Sands¹,

Knepper²

1987

J. Clin. Invest.

154

123

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“…If urea enters the loop then (TF/P) urea/(TF/P) inulin ratio would be higher in the early distal tubule than the late PCT. Conflicting data exist on this point in animals not undergoing saline diuresis (12,14,24); however, most of the observations suggest that recirculation of urea does exist, thus implying that either the descending or ascending thin limb of Henle should be relatively permeable to urea. In the present study, the role of the DLH was examined directly and noted to be as impermeable to urea as previously reported for Na (Table VII).…”

Section: Discussionmentioning

confidence: 99%

“…Micropuncture studies have previously demonstrated that proximal tubular-fluid-to-plasma-urea concentrations are greater than one (12,(14)(15)(16)(17) with most of the value ranging between 1.4 and 1.5. In the absence of active urea secretion this would imply that the PCT is relatively impermeable to urea and is consistent with the Curea of 0.91.…”

Section: Discussionmentioning

confidence: 99%

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Urea transport in the proximal tubule and the descending limb of Henle

Kokko¹

1972

J. Clin. Invest.

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A B S T R A C T Urea transport in proximal convoluted tubule (PCT) and descending limb of Henle (DLH) was studied in perfused segments of rabbit nephrons in vitro.Active transport of urea was ruled out in a series of experiments in which net transport of fluid was zero. Under these conditions the collected urea concentration neither increased nor decreased when compared to the mean urea concentration in the perfusion fluid and the bath.Permeability coefficient for urea (Purea) was calculated from the disappearance of urea-'4C added to perfusion fluid. Measurements were obtained under conditions of zero net fluid movement: DLH was perfused with isosmolal ultrafiltrate (UF) of the same rabbit serum as the bath, while PCT was perfused with equilibrium solution (UF diluted with raffinose solution for fluid [Na] = 127 mEq/liter). Under these conditions Pu,.. per unit length was 3.3±0.4 X 10 cm'/sec (5.3±(0.6 X 10 cm/sec assuming I.D. = 20) in PCT and 0.93±0.4 X 10-7 cm'/sec (1.5±0.5 X 10' cm/sec) in DLH. When compared to previously published results, these values show that the PCT is 2.5 times less permeable to urea than to Na, while the DLH is as impermeable to urea as to Na. These results further indicate that the DLH is less permeable to both Na and urea than the PCT.The reflection coefficient for urea,°urea was calculated as the ratio of induced solution efflux when 95 mOsm/liter of urea was added to the bath, as compared to net fluid movement induced by addition to the bath of equivalent amount of raffinose.°urea in DLH is 0.95±0.4 as compared to 0.91±0.05 in PCT. ourea in DLH is approximately equal to OuNs; however, curea in PCT is higher than ffNa (0.68).

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“…They were anesthetized with sodium pentobarbital (35 mg/kg, i.v.) and prepared for micropuncture of the left kidney as described previously [11]. A carotid ar tery was catheterized for determination of blood pressure and for collection of arterial blood sam ples.…”

Section: Methodsmentioning

confidence: 99%