Present knowledge of the counter-current system in the mammalian kidney

Ullrich, Karl Julius; Kramer, Kürt; Boylan, John W.

doi:10.1016/s0033-0620(61)80001-7

Cited by 155 publications

(49 citation statements)

References 35 publications

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“…Since there is general agreement that, in the presence of antidiuretic hormone, osmotic equilibrium exists between the tubular fluid of the collecting duct and the adjacent interstitial fluid of the papilla [1, 8,23,24], the present results suggest that the jaundiced weanling rat could concentrate urine as well as could its heterozygous litter-mate. It therefore seems reasonable to 240 conclude that the impairment in urine concentration uniformly seen in adult jaundiced rats does not exist as a defect operative from birth.…”

Section: Discussionmentioning

confidence: 58%

The Response of Jaundiced and Non-Jaundiced Weanling Rats to Thirsting

Odell

1968

Pediatr Res

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ExtractLitter-mate homozygous and heterozygous weanling rats of the Gunn strain were thirsted and fasted for 24 hours. The response of the animals to thirsting was compared by analysis of solute content of serum and composition of fluid in the renal medullae. The results are given in tables I and II. When the mean values for weight loss and serum solute concentrations were compared, it was found that the jaundiced rats were able to conserve body water as well as the non-jaundiced rats and to generate equally high concentrations of total solute in the tissue water of the renal medulla. Only two of the twelve jaundiced animals showed evidence of failure to develop the expected hypertonicity of the medullary tissue water. This failure was qualitatively similar to that found in adult jaundiced rats. Despite the presence of higher concentrations of bilirubin in serum, the medullary bilirubin content of the jaundiced weanling rat was only 5 % of the concentration found in adult animals. The sodium and urea concentrations in the renal medullary fluid were correlated (p <0.001) in the homozygous jaundiced rats (table IV and fig. 1). A similar correlation was not found in the non-jaundiced heterozygous animals. This finding suggests that the normal rat kidney has at least two mechanisms for renal transport of urea, one of which is sodium dependent and the other sodium independent and that the latter mechanism is inoperative in the jaundiced weanling rat. SpeculationIn vitro studies of bilirubin have previously suggested that toxicity is exerted by its surface activity on mitochondrial membranes. The examination of renal function in the intact jaundiced animal has revealed the possibility that tubular transport systems for urea and sodium are impaired in the presence of high concentrations of bilirubin in the renal medulla. These transport systems involve the maintenance of concentration gradients of sodium and urea across tubular epithelium. Bilirubin, through its surface activity, could impair the selective permeability of the membranes involved in urea and sodium transport within the renal medulla.

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Section: Discussionmentioning

confidence: 58%

The Response of Jaundiced and Non-Jaundiced Weanling Rats to Thirsting

Odell

1968

Pediatr Res

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“…(Grantham & Burg, 1966) the delivery of increased quantities of dilute fluid causes a loss of water from the collecting duct into the interstitium greater than that which occurs in hydropenia (Berliner & Bennett, 1967). Furthermore, the body fluid expanison caused by infusion of water is associated with increased glomerular filtration rate and decreased tubular reabsorption of sodium (Martino & Earley, 1967); this will also contribute to increased flow in the loop of Henle with possible effects on the medullary content of water and on countercurrent multiplication mechanisms (Ullrich, Kramer & Boylan, 1961).…”

Section: Discussionmentioning

confidence: 99%

The time course of changes in renal tissue composition during water diuresis in the rat

Atherton¹,

Hai²,

Thomas³

1968

The Journal of Physiology

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SUMMARY1. The time course and extent of changes in the composition of renal tissue slices in water diuresis were determined by sacrificing groups of rats before and during the intravenous infusion of dextrose (2.5 g/100 ml.) in amounts sufficient to administer over 2 hr, and subsequently to maintain for up to 74 hr, a positive fluid load of 4 % body weight.2. The corticomedullary osmolal gradient characteristic of the nondiuretic rats was progressively dissipated until, at 74 hr, only papillary tip concentrations were higher than those of other segments.3. The changes in individual constituents followed different time courses: (i) an increase in water content in all segments, particularly the papilla, was almost complete by 1 hr, preceding the maximal increases in urine flow; (ii) a marked decrease in papillary and medullary urea content in the first hour was followed by a slower, progressive decrease leading to an almost complete dissipation of the urea gradient by 74 hr; (iii) small, non-significant decreases in sodium content occurred in all segments in the first hr, followed by a further small, progressive decrease in papillary sodium content; (iv) changes in ammonium and potassium concentrations were mainly related to those in water content, since the contents of these solutes showed only small changes.4. By 2 hr, differences in the rates of decline of osmolal and urea concentrations in urine and papilla led to urinary concentrations significantly lower than papillary values. The steep papilla-urine urea concentration difference became smaller, but remained significant even at 74 hr.5. The findings are discussed in terms of changes in countercurrent mechanisms, particularly as influenced by anti-diuretic hormone.6. The development of papilla/urine urea concentration ratio greater than unity is also considered in terms of passive transport with changes in membrane permeability.

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“…Sodium is presumably pumped from the interior of the cell across the periluminal border (29), and the concentration of sodium within distal tubular cells is probably close to that in proximal tubular cells (30,31). The concentration gradient against which sodium must be transported is therefore similar in cells of the proximal and distal cortical convolutions, though external sodium tends to be higher in the medulla of the kidney than in the cortex, at least during hydropenia (32).…”

Section: Methodsmentioning

confidence: 98%