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Urine concentration and dilution in the rat: Contribution of papillary structures during high rates of urine flow

1978; Elsevier BV; Volume: 13; Issue: 3 Linguagem: Inglês

10.1038/ki.1978.29

1523-1755

M. Martinez-Maldonado, Susan Opava–Stitzer,

Chronic Kidney Disease and Diabetes

Urine concentration and dilution in the rat: Contribution of papillary structures during high rates of urine flow. To examine the contribution of papillary structures to the overall process of urine dilution and concentration at high rates of flow, studies were performed in unilaterally papillectomized kidneys (PX). Comparison of kidney weights in sham-operated and PX rats revealed a significant reduction in total weight of the latter. Papillary length removed was 3045 ± 423 µm. GFR was reduced by 24% and 45% in sham and PX kidneys when compared to their contralateral controls. Under hydropenic conditions, maximal urine concentrating ability (U max ) was comparable in control and sham kidneys but was 59% less in PX kidneys. Fractional sodium excretion during hydropenic conditions was comparable in control and PX kidneys. Nonurea solute [(Na + K) × 2] concentration in the medulla of control and papillectomized kidneys was essentially the same. Free water reabsorption (T c H 2 O ) as a function of osmolar clearance (C Osm ) was comparable in control, sham, and PX kidneys. At C Osm greater than 25%, there was a tencency for T c H 2 O to fall in both control and PX kidneys. Free water clearance (C H 2 O ) during hypotonic saline diuresis rose in almost linear fashion as a function of urine flow (V) without clear-cut differences between control and PX kidneys. There was, however, a tendency for C H 2 O to be slightly higher at any level of V in PX than in control kidneys. These experiments suggest that nephrons with long loops reaching into the papilla and the terminal collecting ducts are not essential for the maximal generation and reabsorption of free water. Concentration et dilution de l'urine chez le rat: Contribution des structures papillaires au cours des debits uriniares eleves. Afin d'evaluer la contribution des structures papillaires au processus global de dilution et de concentration de l'urine au cours des debits urinaires eleves, les effets de la papillectomie (PX) unilaterale ont ete etudies. La comparaison des poids des reins des rats PX avec ceux ayant subi un simulacre d'intervention (sham) a montre une reduction significative du poids total des premiers. La longueur de papille enlevee etait de 3045 ± 423 µm. La filtration glomerulaire etait reduite de 24% chez les sham et 45% chez les PX par comparaison avec le rein contralateral. Dans des conditions d'hydropenie U max est comparable chez les Sham et les controles mais diminue de 59% pour les reins PX. L'excretion fractionnelle de sodium dans les conditions d'hydropenie est comparable pour les reins controles et PX. La concentration des solutes non ureiques [(Na + K) × 2] dans la medullaire des controles et des PX est semblable. La reabsorption d'eau libre (T c H 2 O ), au cours de la diurese hypertonique au sel, exprimee en fonction de la clearance osmolaire (C Osm ), est comparable chez les controles, les sham et les PX. A C Osm superieure a 25% il y a une tendance de T c H 2 O a diminuer a la fois chez les controles et les PX. La clearance de l'eau libre (C H2O ) au cours de la diurese hypotonique au sel augmente d'une facon presque lineaire en fonction du debit urinaire (V) sans qu'apparaisse de difference nette entre les reins PX et les controles. II y a, cependant, une tendance de C H 2 O a etre legerement superieure, pour toutes les valeurs de V, pour PX que pour les reins controles. Ces experiences suggerent que les nephrons a anses longues atteignant la papille et les canaux collecteurs a anses longues ne sont pas indispensables a l'excretion et la reabsorption maximales d'eau libre.