Solute and water flows in thin limbs of Henle's loop in the hamster kidney.
01 Mar 1970-American Journal of Physiology (American Physiological Society)-Vol. 218, Iss: 3, pp 824-831
TL;DR: There was no change of the inulin TF/P along the first millimeter of thin ascending limb, a result that rules out hypotheses of hypertonic urine formation requiring the loops to remove water from the interstitium and support for the countercurrent- multiplier hypothesis.
Abstract: MARSH, DONALD J. Solute and water flows in thin limbs of Henle’s loop in the hamster kidney. Am. J. Physiol. 218(3) : 824433 1. 1970. -Collections were made from two sites in single thin limbs on the surface of the exposed hamster papilla. There was no change of the inulin TF/P along the first millimeter of thin ascending limb, a result that rules out hypotheses of hypertonic urine formation requiring the loops to remove water from the interstitium. In the same specimens osmolality, Na+, and K+ concentrations fell as fluid flowed from the bend of the loop up the ascending limb, but there was net urea entry into the tubular fluid. These results were interpreted as support for the countercurrent-multiplier hypothesis. Similar experiments in descending limbs revealed net entry of urea to tubular fluid as it flowed down toward the bend, but were inconclusive on the question of net entry of NaCl. Urea concentration in tubular fluid at the bend was lower than in adjacent vasa recta blood, so that all urea movement can be accounted for by passive movement down concentration gradients. ity and NaCl concentrations to values lower than in adjacent descending limbs, which simply equilibrate with the interstitial fluid.
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TL;DR: This model is based largely on transport characteristics obtained by perfusing isolated segments of rabbit nephrons in vitro, and allows the entire system to operate by passive diffusion of NaCl out of the thin ALH.
381 citations
TL;DR: Concentration of urine in a central core model of the renal counterflow system with Urea cycling, regulated by ADH, allows active Na + transport in the outer medulla and cortex to be used for concentration in the inner medulla.
331 citations
TL;DR: The renal medulla develops very differently among species, being more prominent in those with a high urinary concentrating capacity, and attempts to correlate structure and function must consider loops of Henle, collecting ducts, vessels, interstitium, and pelvis.
Abstract: The renal medulla develops very differently among species, being more prominent in those with a high urinary concentrating capacity. Attempts to correlate structure and function must consider loops of Henle, collecting ducts, vessels, interstitium, and pelvis. Two types of loops of Henle, long and short, are distinguished. Numerical relationships between both differ among species. Based on the epithelial lining a short loop consists of a thick descending limb (pars recta of proximal tubule), a thin descending limb, and a thick ascending limb. Long loops, in addition, have a thin ascending limb; their descending thin limbs are different from those of short loops and are site of considerable interspecies differences. Collecting ducts form in the cortex by joining several nephrons. Patterns with and without arcade formation are distinguished. On entering inner medulla, collecting ducts fuse successively. Collecting duct epithelium consists of principal and intercalated cells whose individual functions are subject to debate. Blood vessels are arranged in a very strict pattern reflecting that, in addition to nourishment, unique requirements in maintaining the corticomedullary osmotic gradient are to be met. Ultrastructural organization of medullary vessels is less specific compared to cortical vessels. Two types of renal medulla are distinguished. The simple type has vascular bundles consisting only of de- and ascending vasa recta; in the complex type, descending thin limbs of short loops are also integrated into vascular bundles. Functional implications of this difference are considerable. Striking interspecies differences also occur in the renal pelvis.
225 citations
TL;DR: It is concluded that active transport of salt by the t ALH was not detected by the experimental protocol of the current studies, and that the unique membrane characteristics of tALH allows for generation of osmotic gradients on purely passive mechanisms when perfused with isosmolal salt solutions in a bath with appropriate salt and urea concentrations.
Abstract: Studies were designed to examine whether the thin ascending limb of Henle (tALH) decreases its luminal solute concentration by an active or a passive transport process In all experiments isolated segments of rabbit tALH were perfused in vitro When tubules were perfused with solutions identical to the bath, active transport of NaCl was excluded by the following: (a) osmolality of the collected fluid remained unchanged and the same as the bath (b) net water reabsorption could not be demonstrated, and (c) transtubular potential difference was zero Isotopic permeability coefficients (x 10(-5) cm s-1) were calculated from the disappearance rate of the respective isotope added to the perfusate These values indicate that tALH is moderately permeable to [14C]urea (697 +/- 195) while having a higher permeability to 22Na (255 +/- 18) and [not readable: see text]Cl (117 +/- 91) than any other segment similarly studied The influx (bath-to-lumen) isotopic permeabilities were not statistically different from the above efflux permeabilities Osmotic water permeability was immeasurably small When tALH were perfused with a 600 mosmol/liter solution predominantly of NaCl against a 600 mosmol/liter bath in which 50% of osmolality was NaCl and 50% urea (to simulate in vivo papillary interstitium), the collected fluid osmolality was decreased significantly below that of the bath (300 mosmol/liter/mm of tubule) The decrease in osmolality was due to greater efflux of NaCl as compared to influx of urea We conclude that active transport of salt by the tALH was not detected by the experimental protocol of the current studies, and that the unique membrane characteristics of tALH allows for generation of osmotic gradients (lumen less concentrated than adjacent surroundings) on purely passive mechanisms when perfused with isosmolal salt solutions in a bath with appropriate salt and urea concentrations These findings are consistent with the passive counter-current model previously proposed from this laboratory
199 citations
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...of Marsh (3) have also shown that the osmolality and the Na concentration in the tALH are lower than the...
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TL;DR: The IMCD displays axial heterogeneity with respect to urea permeability, with a high permeability only in its distal two-thirds; and because the u Andrea permeability and surface area of the PSE are relatively small, passive transport across it is unlikely to be a major source of urea to the inner medullary interstitium.
Abstract: 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 (X 10(-5) cm/s) in rat IMCDs were: outer third of inner medulla (IMCD1), 1.6 +/- 0.5; middle third (IMCD2), 46.6 +/- 10.5; and inner third (IMCD3), 39.1 +/- 3.6. Mean permeability coefficients in rabbit IMCDs were: IMCD1, 1.2 +/- 0.1; IMCD2, 11.6 +/- 2.8; and IMCD3, 13.1 +/- 1.8. The rabbit PSE was dissected free from the underlying renal inner medulla and was mounted in a specially designed chamber to measure its permeability to urea. The mean value was 1 X 10(-5) cm/s both in the absence and presence of vasopressin (10 nM). Morphometry of renal papillary cross sections revealed that the total surface area of IMCDs exceeds the total area of the PSE by 10-fold in the rat and threefold in the rabbit. We conclude: the IMCD displays axial heterogeneity with respect to urea permeability, with a high permeability only in its distal two-thirds; and because the urea permeability and surface area of the PSE are relatively small, passive transport across it is unlikely to be a major source of urea to the inner medullary interstitium.
150 citations
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TL;DR: A theory concerning the origin of the frog skin potential is put forward based on observations and the assumption that the active transport of sodium is located at the inward-facing membrane of the epithelial cells.
Abstract: Summary.
1. The outside of the isolated frog skin in the absence of penetrating anions behaves over a wide range of concentrations as a sodium electrode, while the inward-facing surface behaves like a potassium electrode.
2. A theory concerning the origin of the frog skin potential is put forward based on these observations and the assumption that the active transport of sodium is located at the inward-facing membrane of the epithelial cells.
3. Reasons are given for the hypothesis that the active transport of sodium in reality is a forced exchange of sodium against potassium.
1,097 citations
TL;DR: All parts of the nephron were relatively impermeable to mannitol but were permeable to urea, which is consistent with what would be predicted if the driving force of the countercurrent system were a sodium pump in the ascending limb of the loop of Henle, although such a pump was not demonstrated.
Abstract: MORGAN, TREFOR, AND ROBERT MT. BERLINER. Permeability of the loop of Henle, uasu recta, and collecting duct to water, urea, and sodium. Am. J. Physiol. 215(l): 108-115. 1968.-The permeability of the loops of Henle, collecting ducts, and vasa recta have been studied by free-flow perfusion. When ADH was absent the diffusional permeability coefficient for THO in the descending limb (DL) was I 19 ZII 14 (SE) cm se0 X lo-“, ascending limb (AL) 50 =t 4.5 collecting duct (CD) 45 =t 3.1, and vasa recta (VR) at least 192 & 20. ADH increased the value for collecting ducts to 87 + 7 without changing the other values. The diffusional permeability coefficients for urea were DL 13 =t 3.0; AL 14 =t 2.0; CD 20 + 1.3; and VR 47 + 3.3. ADH increased the permeability of the CD (30 + 2.4) without affecting the other structures. The permeability of the descending limb changed before the hairpin bend. Net water flux was DL 58 + 6.2 nliters cmm2 milliosmoF min-I, AL 4.4 + 1.1; CD (no ADH) 4.2 zk 2.2; CD (ADH) 30 + 2.6. All parts of the nephron were relatively impermeable to mannitol but were permeable to urea. NaCl did not enter the collecting duct or ascending limb but entered the descending limb of Henle’s loop. These observations are consistent with what would be predicted if the driving force of the countercurrent system were a sodium pump in the ascending limb of the loop of Henle, although such a pump was not demonstrated in this preparation.
204 citations
TL;DR: The differences between ascending and descending limbs of the loop of Henle suggest that the thin segment functions as a countercurrent mu1 tiplier in the production of the hypertonic medulla.
Abstract: .JAMISON, REX L., CLEAVES M. BENNETT, AND ROBERT W. BERLINER. Countercurrent multiplication by the thin loops of Henle. Am. J. Physiol. 2 I 2 (2) : 357-366. I g67.-The contribution of the thin loops of Henle and the vasa recta to the production of the hypertonicity of the mammalian renal medulla was investigated in rats using a modified version of the partial nephrectomy technique of Sakai et al. In the region between 2 and 4 mm from the tip of the papilla, no significant difference in osmolality was found between adjacent descending limbs or between descending limbs and adjacent hairpin turns. In contrast, ascending limbs were found to have a significantly lower osmotic pressure than adjacent descending limbs (mean difference I I 7 milliosmols). A lower concentration of sodium accounted for most of this difference. Fluid from the descending limbs of the loops had a significantly higher osmolality than plasma from the descending vasa recta, but roughly equal to that of plasma from the ascending rasa vecta. In this region of the medulla, blood entering through the descending vasa recta appears to lag in attaining osmotic equilibrium with its surroundings, a finding consistent with the behavior of a passive countercurrent exchanger. The differences between ascending and descending limbs of the loop of Henle, on the other hand, suggest that the thin segment functions as a countercurrent mu1 tiplier in the production of the hypertonic medulla.
115 citations
TL;DR: It is suggested that the ascending limb potential is a streaming potential, but that the collecting duct potential reflects active ion transport, and that neither segment transports salt actively.
Abstract: Saline solutions isolated between oil droplets within the lumen of thin limbs of Henle9s loops remained at constant volume, while raffinose solutions underwent a continuous volume increase with time. After equilibrium, composition of the NaCl perfusates with respect to osmolality and Na and Cl concentrations became similar to that of vasa recta plasma. These results were identical for both ascending and descending limbs and suggest that neither segment transports salt actively. Descending limbs and vasa recta were isopotential under all conditions; the ascending limb during antidiuresis is 9 mv negative, the collecting ducts 17 mv negative. Ascending limb negativity was abolished by osmotic diuresis or stopped-flow microperfusion with saline. Measurement of ion concentrations showed that the ascending limb potential of antidiuresis is not a diffusion potential, and that its disappearance during osmotic diuresis is not due to the appearance of a diffusion potential of countersign. We suggest that the ascending limb potential is a streaming potential, but that the collecting duct potential reflects active ion transport.
98 citations
TL;DR: Using micropuncture techniques, fluid was collected from loops of Henle at the tip of the renal papilla in anesthetized hamsters and Psammomys, and its composition compared with that of collecting blood samples using conventional methods.
Abstract: Using micropuncture techniques, fluid was collected from loops of Henle at the tip of the renal papilla in anesthetized hamsters and Psammomys, and its composition compared with that of collecting ...
90 citations