Sekretion von Wasserstoffionen in den Sammelrohren der S�ugetierniere

Kj, Ullrich; Fw, Eigler

doi:10.1007/bf00361735

Cited by 59 publications

(6 citation statements)

References 11 publications

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“…More than 98%7 of the total ammonia present in fluid at any physiologic pH is in the form NH +; most of the NH3 diffusing into the nephron must therefore be instantaneously converted to NH4+, but the extent of this conversion will increase as urinary acidity increases, so that the total ammonia transported by the time [NH3] is about the same inside and outside the lumen will be directly proportional to [H+] of luminal fluid. The bulk of the ammonia is assumed to be transported at a site in the nephron at or below that where luminal contents are acidified; this process has been supposed to consist of exchange of the H+ secreted for Na+ reabsorbed (41) and assigned by most investigators to the distal tubule (42)(43)(44)(45)(46)(47) (Table II) as urinary flow rate rises to its ceiling strongly supports the diffusion hypothesis. Since 99% or more of the ammonia present in any fluid of pH less than 7 is in the form of NH.+, it follows that as NH3 diffuses into the lumen, it will be converted almost quantitatively to NH4+ by combining with H+ according to the reaction: H+ + NH., diffusing in > NH4+.…”

Section: Methodsmentioning

confidence: 77%

“…The experiments described were conducted under conditions of forced diuresis and usually of acidosis as well, so reabsorption of NH3 might possibly or even probably begin considerably higher in the collecting duct during antidiuresis in hamsters. The postulated generation of H+ through back-diffusion of NH3 can fully account for the apparent discrepancies in the locus of H+-secretion between the reports of Ullrich and his colleagues (45,48) and those of investigators working with other mammals and with amphibia (42)(43)(44)47 (45,46,48). This evidence is difficult to reconcile either with limitation of diffusion or with a rise toward the papilla of interstitial [NH3] sufficient to prevent backdiffusion, since in both cases He should be consumed instead of generated in the collecting duct as NH3 continued to diffuse into the luminal fluid.…”

Section: )mentioning

confidence: 90%

“…Direct analysis has recently shown that luminal fluid is further acidified within the collecting ducts (45,46,48), but the process does not necessarily consist entirely or principally of H+-secretion proper. Ullrich and his colleagues found that H+ and ammonia were added to, and Na+ reabsorbed from, the lumen of the nephron between the farthest zone to which the catheter could be passed and a site in the collecting duct located closer to the papilla.…”

Section: )mentioning

confidence: 99%

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Diffusion of Gases Out of the Distal Nephron-Segment in Man. I. Nh3*

Woeber¹,

Reid²,

Kiem³

et al. 1963

J. Clin. Invest.

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Physiologic variation in rate of urine flow in mammals is ascribed principally to reabsorption from distal tubules and collecting ducts of a varying quantity of nearly solute-free water (1-4). Water reabsorption is brought about by bulk flow or diffusion (5-8) incited by the difference in osmotic pressure between the luminal contents and the hypertonic fluid of the adjacent renal medullary interstitium, a process promoted by the action of endogenous vasopressin upon the permeability of the intervening membranes (7, 9). Elaboration of urine much less than maximally dilute increases the osmolality of luminal fluid as it progresses down the most distal portion of the nephron; the result must be to raise the diffusion pressure of all substances dissolved in luminal fluid.Two highly diffusible substances, the gases NH3 and CO2, are present in solution in luminal fluid together with their hydrated forms NH4OH and H2CO3, in turn in equilibrium, so as to constitute two buffer systems, with the ionized species NH4+ and HCO3-, respectively. If, as a result of the reabsorption of solute-free water, these gases are reabsorbed by diffusion, the existence and magnitude of the process should be reflected in alterations in the acid-base composition of voided urine no less than by changes in the rate of excretion of total ammonia and total carbon 1962-63. dioxide. Examination of the effects of water diuresis in normal man upon these various parameters has provided indirect evidence that the gases NH3 and CO2 do in fact diffuse out of the nephron's lumen during antidiuresis (10-12).1 This communication presents evidence that the rate of urinary ammonia excretion is largely determined by factors affecting the net diffusion of the free base NH3 into the distal portion of the nephron; the evidence further indicates that some NH3, having diffused into the lumen, subsequently diffuses back into the renal interstitium as a result of reabsorption of water from the lumen. METHODSExperimental design. Subjects were 12 healthy adult male volunteers whose rate of urinary flow was caused to vary between 1 ml per minute and the physiologic ceiling by controlled water-drinking. Serial, timed urine collections were made at intervals of about 12 minutes by voluntary emptying of the bladder. The individual experiments, generally comprising 20 or more collections, were begun about 8 a.m. in subjects who fasted overnight and remained upright during and for at least an hour before the experiment. When alkaline or mark-1 "Ammonia" means total ammonia. NH, includes NH4OH when ratios of the buffer species are in question, and HCO3 includes anhydrous CO, in the analagous context. NH4, is not considered a form of buffered H' except that "total H`" excretion includes NH,+.It has been inferred from experiments on toad bladder and other membranes (5) that vasopressin promotes osmotic movement of water out of the nephron by hydraulic flow through pores rather than by diffusion. The facts about the toad bladder are disputed (8), and there is no direct info...

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Section: Methodsmentioning

confidence: 77%

Section: )mentioning

confidence: 90%

Section: )mentioning

confidence: 99%

See 1 more Smart Citation

Diffusion of Gases Out of the Distal Nephron-Segment in Man. I. Nh3*

Woeber¹,

Reid²,

Kiem³

et al. 1963

J. Clin. Invest.

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“…Obviously, quantitative comparison of our data with rat micropuncture data is not possible. The rise in potassium, titratable acid, and ammonium excretion following ethacrynic acid suggests that sodium reabsorption occurred distal to the loop of Henle (24)(25)(26)(27)(28)(29)(30)(31)(32)(33)(34)(35)(36). Hence, a portion of sodium rejected proximal to the distal tubule and collecting duct would not have been excreted.…”

Section: III B a Typical Study Is Illustrated Inmentioning

confidence: 99%

Effects of Ethacrynic Acid (a New Saluretic Agent) on Renal Diluting and Concentrating Mechanisms: Evidence for Site of Action in the Loop of Henle*

Goldberg¹,

McCurdy²,

Foltz³

et al. 1964

J. Clin. Invest.

155

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“…The inner medullary collecting duct (IMCD)' absorbs HCO3, secretes ammonia, and titrates luminal buffers (1)(2)(3)(4)(5)(6). How-exchanger has been postulated based on stilbene-sensitive HCO-absorption (3), and changes in cell pH in cells cultured from the inner medulla (20, 21).…”

Section: Introductionmentioning

confidence: 99%

Basolateral membrane sodium-independent Cl-/HCO3- exchanger in rat inner medullary collecting duct cell.

Star¹

1990

J. Clin. Invest.

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Previous studies have shown that the middle third of the rat inner medullary collecting duct (IMCD-2) secretes protons despite the absence of intercalated cells, the cell thought to secrete protons in other portions of the collecting duct. A new cell, the IMCD cell, is the predominant cell in IMCD-2. The mechanism responsible for base exit in the IMCD cell was characterized by measuring cell pH of isolated perfused tubules with 2',7'-bis-(carboxyethyl)-5,6-carboxyfluorescein. Reduction of bath HCO3 caused a significant and reversible decrease in cell pH, whereas a similar change in luminal HCO3 had a significantly smaller effect, indicating that the HCO3/ H+ permeability of the basolateral membrane is much larger than the apical membrane. The rate of cell acidification induced by reduction in bath HCO3, a measure of basolateral HCO3 transport, was significantly decreased in the absence of bath and lumen Cl. Decreases in bath Cl caused a significant and reversible increase in cell pH, which was not changed significantly by complete removal of Na from perfusate and bath, but was significantly inhibited by basolateral 4'5'-diisothiocyanostilbene-2,2'-disulfonic acid. A chemical voltage clamp did not inhibit the rate of cell alkalinization after bath Cl removal, indicating that Cl-/HCOj exchange is not via parallel C1 and HCO3 conductances. Cell pH was measured in single cells by low-light-level imaging to show that most cells contain the chloride-dependent HCO3 pathway. We conclude that the rat IMCD cell possesses a basolateral Na-independent

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Sekretion von Wasserstoffionen in den Sammelrohren der S�ugetierniere

Cited by 59 publications

References 11 publications

Diffusion of Gases Out of the Distal Nephron-Segment in Man. I. Nh3*

Diffusion of Gases Out of the Distal Nephron-Segment in Man. I. Nh3*

Effects of Ethacrynic Acid (a New Saluretic Agent) on Renal Diluting and Concentrating Mechanisms: Evidence for Site of Action in the Loop of Henle*

Basolateral membrane sodium-independent Cl-/HCO3- exchanger in rat inner medullary collecting duct cell.

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