Messungen des Ammoniakdruckes in den corticalen Tubuli der Rattenniere

Oelert, H.; Uhlich, E.; Hills, A. Gorman

doi:10.1007/bf00380846

Cited by 21 publications

(14 citation statements)

References 21 publications

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“…The finding that the ammonia content of fluid obtained near the beginning of the distal tubule is lower than that of the proximal tubule has not been reported previously and suggests that the permeabilities of the nephron segments proximal to these two sites of micropuncture are different. These results are in contrast to previous studies (8)(9)(10), which suggested that ammonia was in diffusion equilibrium throughout the cortex. Indeed, Oelert et al (10) reported that the ammonia concentrations in renal venous blood, proximal tubule, and distal tubule fluid were not measurably different.…”

Section: Discussioncontrasting

confidence: 99%

“…These results are in contrast to previous studies (8)(9)(10), which suggested that ammonia was in diffusion equilibrium throughout the cortex. Indeed, Oelert et al (10) reported that the ammonia concentrations in renal venous blood, proximal tubule, and distal tubule fluid were not measurably different. The basis for the apparent difference in the results obtained in the present study and that of Oelert et al (10) may be in the methodology employed in the two efforts.…”

Section: Discussioncontrasting

confidence: 99%

“…The basis for the apparent difference in the results obtained in the present study and that of Oelert et al (10) may be in the methodology employed in the two efforts. First, tubule fluid samples were obtained from different segments of the same nephron in the (10) found similar tubule fluid pH and ammonia values at proximal and distal micropuncture sites. Another difference in the two studies is that the determinants for estimating the free ammonia concentration (tubule fluid pH, and total ammonium concentration) were measured by different techniques.…”

Section: Discussioncontrasting

confidence: 78%

“…Indeed, Oelert et al (10) reported that the ammonia concentrations in renal venous blood, proximal tubule, and distal tubule fluid were not measurably different. The basis for the apparent difference in the results obtained in the present study and that of Oelert et al (10) may be in the methodology employed in the two efforts. First, tubule fluid samples were obtained from different segments of the same nephron in the (10) found similar tubule fluid pH and ammonia values at proximal and distal micropuncture sites.…”

Section: Discussionmentioning

confidence: 99%

“…Further, most studies indicate that ammonia moves by diffusion into the tubule lumen where it is ionized and subsequently entrapped as ammonium. Based on both indirect (8,9) and direct evidence (10), it has long been postulated that there is no limitation to the movement of ammonia across cell membranes and that it exists at diffusion equilibrium conditions. However, evidence suggests that this theory may not apply to all structures within the kidney.…”

Section: Introductionmentioning

confidence: 99%

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Contribution of individual superficial nephron segments to ammonium handling in chronic metabolic acidosis in the rat. Evidence for ammonia disequilibrium in the renal cortex.

Simon¹,

Martin²,

Buerkert³

1985

J. Clin. Invest.

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Ammonia entry along surface nephron segments of rats was studied with micropuncture techniques under control and chronic metabolic acidosis conditions. Tubule fluid was collected successively from sites at the end and beginning of the distal tubule and at the end of the proximal tubule of the same nephron. During chronic metabolic acidosis, ammonium excretion doubled. As anticipated, the ammonium concentration (TFNHO3 was significantly higher in proximal tubule fluid during acidosis, and ammonium delivery to end proximal sites increased from 19.4±2.3 to 34.0±3.2 pmol/min (P < 0.001). Although chronic acidosis did not affect TFNW at the beginning of the distal tubule, ammonium delivery to the end of the distal tubule increased from 5.72±0.97 to 9.88±0.97 pmol/min. In both control and acidotic groups ammonium delivery was lower (P < 0.001) to end distal sites than to end proximal sites, indicating net loss in the intervening segment. This loss was greater during chronic metabolic acidosis (23.9±33 vs. 13.6±2.0 pmol/min in controls, P < 0.025). In both groups net entry of ammonia, in similar amounts, occurred along the distal tubule (P < 0.05). In situ pH averaged 6.80±0.05 at end proximal tubule sites and fell to 6.54±0.08 at the beginning of the distal tubule (P < 0.005). Chronic metabolic acidosis did not affect these measurements. The calculated free ammonia at the end of the proximal tubule rose from 93±2.2 to 21±9 iM (P < 0.005) during chronic metabolic acidosis, and was also higher at beginning distal sites during acidosis (8.8±2.4 vs.2.7±0.7 uM in controls, P < 0.05). In both groups ammonia values for the beginning distal tubule fluid were lower than for end proximal tubule fluid. Thus, loss of ammonium in the loop segment is enhanced by chronic metabolic acidosis. Distal entry of ammonia is markedly less than along the proximal tubule and does not change in chronic metabolic acidosis, and ammonia permeabilities for the proximal and distal segments of surface nephrons seem different.

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Section: Discussioncontrasting

confidence: 99%

Section: Discussioncontrasting

confidence: 99%

Section: Discussioncontrasting

confidence: 78%

Section: Discussionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

See 3 more Smart Citations

Contribution of individual superficial nephron segments to ammonium handling in chronic metabolic acidosis in the rat. Evidence for ammonia disequilibrium in the renal cortex.

Simon¹,

Martin²,

Buerkert³

1985

J. Clin. Invest.

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Responses to reversed NH₃ and NH₄⁺ gradients in a teleost (Ictalurus punctatus), an elasmobranch (Raja erinacea), and a crustacean (Callinectes sapidus): Evidence for NH₄⁺/H⁺ exchange in the teleost and the elasmobranch

Cameron

1986

J. Exp. Zool.

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Ammonia excretion rates of channel catfish, Ictalurus punctatus, little skate (Raja erinacea), and blue crab (Callinectes sapidus) were measured in experimental regimes which permitted simultaneous assessment of the partial pressure gradients for nonionized NH3 and the chemical concentration gradients of NH4+. Under conditions of low external ammonia, the average ammonia excretion was +295 microM kg-1 h-1 for catfish, +149 microM kg-1 h-1 for blue crabs, and +59 microM kg-1 h1 for skates with partial pressure gradients of +72.5 mu Torr, +413 mu Torr, and +24.4 mu Torr, respectively; and [NH4+] gradients of +189 microM l-1, +643 microM l-1, and +107 microM l-1 (positive indicating greater from inside to medium). When the external ammonia was increased to 1.15 mM l-1, both gradients were reversed, and the net ammonia movement was initially from the external water into all three species. In the catfish the inward movement ceased, however, and ammonia excretion eventually resumed in the face of reversed gradients of both NH3 partial pressure and [NH4+]. Unidirectional Na+ influx, indicative of a Na+/NH4+ exchange, did not increase. The ammonia data, changes in titratable acidity, and net apparent H+ efflux were all consistent with a linked extrusion of internal NH4+ for external H+. Incorporation of such an exchange into a computer simulation model of the ammonia equilibrium and exchange system duplicated the experimental data. Other hypotheses failed to match experimental data, or failed to predict internal ammonia levels lower than outside. In the crab, internal ammonia levels rose rapidly to concentrations and partial pressures above the external medium until excretion was reestablished, with no evidence of maintenance of a reversed gradient. In the skate, internal concentrations rose appreciably in the first hour and continued to rise for 6-8 h, with no resumption of ammonia excretion. The interspecies differences appear to be due at least partly to differences in ammonia permeability of the gills.

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Acid-Base Regulation: Interrelationships Between Gaseous and Ionic Exchange

Heisler

1990

Vertebrate Gas Exchange

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Messungen des Ammoniakdruckes in den corticalen Tubuli der Rattenniere

Cited by 21 publications

References 21 publications

Contribution of individual superficial nephron segments to ammonium handling in chronic metabolic acidosis in the rat. Evidence for ammonia disequilibrium in the renal cortex.

Contribution of individual superficial nephron segments to ammonium handling in chronic metabolic acidosis in the rat. Evidence for ammonia disequilibrium in the renal cortex.

Responses to reversed NH₃ and NH₄⁺ gradients in a teleost (Ictalurus punctatus), an elasmobranch (Raja erinacea), and a crustacean (Callinectes sapidus): Evidence for NH₄⁺/H⁺ exchange in the teleost and the elasmobranch

Acid-Base Regulation: Interrelationships Between Gaseous and Ionic Exchange

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Messungen des Ammoniakdruckes in den corticalen Tubuli der Rattenniere

Cited by 21 publications

References 21 publications

Contribution of individual superficial nephron segments to ammonium handling in chronic metabolic acidosis in the rat. Evidence for ammonia disequilibrium in the renal cortex.

Contribution of individual superficial nephron segments to ammonium handling in chronic metabolic acidosis in the rat. Evidence for ammonia disequilibrium in the renal cortex.

Responses to reversed NH3 and NH4+ gradients in a teleost (Ictalurus punctatus), an elasmobranch (Raja erinacea), and a crustacean (Callinectes sapidus): Evidence for NH4+/H+ exchange in the teleost and the elasmobranch

Acid-Base Regulation: Interrelationships Between Gaseous and Ionic Exchange

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Responses to reversed NH₃ and NH₄⁺ gradients in a teleost (Ictalurus punctatus), an elasmobranch (Raja erinacea), and a crustacean (Callinectes sapidus): Evidence for NH₄⁺/H⁺ exchange in the teleost and the elasmobranch