Urinary Concentration in the Papillary Collecting Duct of the Rat

Oliver, Richard E.; Roy, Denis; Jamison, Rex L.

doi:10.1172/jci110426

Cited by 40 publications

(23 citation statements)

References 17 publications

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“…Removal of the ureter would abolish intermittent flow and impair papillary hypertonicity. If the portion of the ureter overlying the papilla is paralyzed but not removed, however, urinary osmolality does not fall, even though intermittent flow in papillary structures is abolished (1). Thus, it is the intactness of the pelvic ureter rather than its contractility that is key to its contribution to papillary hypertonicity.…”

Section: Discussionmentioning

confidence: 99%

“…We recently found that if the ureter is severed just beyond the tip of the renal papilla, urinary osmolality falls (1); this suggested that exchange of either water or solute between urine and renal parenchyma in the renal pelvis subserves urinary concentration. In 1966, Gertz et al (2) reported evidence for exchange of water and solute across the papillary epithelium between the papilla and an artificial fluid superfusing the renal pelvis.…”

Section: Introductionmentioning

confidence: 99%

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Examination of transepithelial exchange of water and solute in the rat renal pelvis.

Bargman¹,

Leonard²,

McNeely³

et al. 1984

J. Clin. Invest.

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Abstract. Severance of the ureter beyond the renal papilla causes a fall in urinary osmolality, which suggests that exchange of water or solute between urine and renal parenchyma normally occurs in the intact renal pelvis. We examined water and solute flux in the renal pelvis with micropuncture and microcatheterization techniques. Four groups of antidiuretic rats were studied. Group I (n = 17) underwent micropuncture through the intact contracting ureter. Urine samples were obtained at the papillary tip, and in the pelvis beside the base of the extrarenal papilla. Urinary osmolality at the base, 880±97 mosmol/kg H20 (mean±SE), was less than that at the tip, 1,425±104i mosmol/kg H20 (P < 0.005). In group II (n = 24), samples were analyzed for inulin and osmolality. In 15 rats (group IIA), comparison was made between base and tip samples. In thei other nine animals (group IIB), comparisons were made among base, tip, and bladder samples and urea was also measured. In group II (A and B combined) urine-to-plasma (U/P) osmolality was lower at the base, 4.31±0.27, than at the tip, 6.08±0.23 (P < 0.001), and U/P inulin was lower at the base, 192±25, than at the tip, 306±16 (P < 0.001). In group IIB, the bladder urine had a lower U/P osmolality, 5.27±0.25, than the tip, 6.01±0.31 (P < 0.02). The U/P urea was 59±10.6 (base), 98±9.4 (tip) (base vs. tip, P < 0.05), and 81±6.5 (bladder, P < 0.005, compared with tip). In group III (n = 8), samples were A preliminary report of these findings has been published in abstract form: Leonard, S., and R. Jamison. 1983 obtained by microcatheter from the fornices, the deepest intrarenal extensions of the pelvis, and compared with samples at the tip. Urinary osmolality was lower in the fornix, 646±106 mosmol/kg H20, than at the tip, 1,296±99 mosmol/kg H20 (P < 0.001). Similarly, U/P inulin was lower in the fornix, 48±14, than at the tip, 128±12 (P < 0.001). The lower U/P inulin in the pelvic urine is the result of either the addition of fluid to the pelvis, or the backleak of inulin across the epithelium lining the pelvis. To verify that the pelvic epithelium was impermeable to inulin, in group IVA (n = 4) the left renal pelvis was superfused with a solution of chemical inulin. Cumulative absorption of inulin from the left kidney was 0.15±0.08% of that superfused. Using ['4C]inulin in group IVB (n = 3), similar results were obtained (0.05±0.02%).These findings indicate that in the renal pelvis, fluid is added to urine after it emerges from the collecting ducts. We suggest that reflux of hyperosmotic urine over the renal papilla creates a transepithelial gradient for the flux of water into the pelvis. A model that incorporates diffusive and convective forces for water and solute transport is proposed to account for these findings.

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Section: Discussionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Examination of transepithelial exchange of water and solute in the rat renal pelvis.

Bargman¹,

Leonard²,

McNeely³

et al. 1984

J. Clin. Invest.

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show abstract

“…While several experiments support this conclusion (Gertz et al, 1966;Schmidt-Nielsen et al, 1970, 1980) the magnitude of urea or water reentry from pelvis to papillary interstitium has never been quantified. Recently developed techniques to measure CD fluid composition through the intact ureter (Oliver et al, 1982) should be able to determine the difference in osmolarity between the fluid in the papillary CD and in the pelvis. A comparison of these measurements with the predictions of the present simulation studies would allow conclusions about the nature of the pelvic reabsórbate and its role for the concentrating mechanism.…”

Section: Discussionmentioning

confidence: 99%

“…It is important to emphasize that this architecture is identical in rat and rabbit (Section 2.2). 2) Recent direct and indirect evidence for the importance of high pelvic urea concentrations and its possible (but not proven) reflux into the medullary interstitium (Bonventre et al, 1978Schütz and Schnermann, 1972;Gertz et al, 1966;Schmidt-Nielsen et al, 1970,1980Oliver et al, 1982). High pelvic urea concentrations have been measured in rat and rabbit; in all mammalian species, the papilla is surrounded by the pelvic cavity (Kriz, 1981).…”

Section: Introductionmentioning

confidence: 99%

Renal countercurrent system: Role of collecting duct convergence and pelvic urea predicted from a mathematical model

1983

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Abstract.A differential equation model of the renal countercurrent system has been developed and physiological data from nephron segments were incorporated together with recently suggested urea recycling from renal pelvis to inner medulla and, particularly, an exponential reduction in the number of collecting tubules towards the renal papilla. The role of these features for the countercurrent concentrating mechanism has been studied by simulation runs. The computations, using the multiple shooting method, provide predictions about concentration profiles for salt and urea in tubes (nephron segments) and in the central core along the entire medullary countercurrent system. The results indicate that this model, without active salt or urea transport in the inner medulla, yields concentration gradients along the medullary axis compatible with those measured in the tissue.

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“…Second, the volume flow rate emerging from the final collecting duet into the pelvis» exceeds a certain bound [36]:…”

mentioning

confidence: 99%

The kidney model as an inverse problem

Breinbauer¹,

Lory

1991

Applied Mathematics and Computation

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The mammalian kidney is modeled by a multipoint boundary-value problem for a System of nonlinear ordinary differential equations. A corresponding inverse problem is presented, which allows the rigorous judgement of the potential of the given modeling technique. For its numerical Solution a discretization is proposed, which is tailor-made for kidney models. It leads to a nonlinear-programming problem with nonlinear equality and inequality constraints. The suggested methods are applied to current research problems in renal physiology.

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Urinary Concentration in the Papillary Collecting Duct of the Rat

Cited by 40 publications

References 17 publications

Examination of transepithelial exchange of water and solute in the rat renal pelvis.

Examination of transepithelial exchange of water and solute in the rat renal pelvis.

Renal countercurrent system: Role of collecting duct convergence and pelvic urea predicted from a mathematical model

The kidney model as an inverse problem

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