Chronic hyperkalemia impairs ammonium transport and accumulation in the inner medulla of the rat

Thomas D. DuBose, David Good

Research output: Contribution to journalArticle

38 Citations (Scopus)

Abstract

Previously we demonstrated in rats that chronic hyperkalemia had no effect on ammonium secretion by the proximal tubule in vivo but that high K+ concentrations inhibited ammonium absorption by the medullary thick ascending limb in vitro. These observations suggested that chronic hyperkalemia may reduce urinary ammonium excretion through effects on medullary transport events. To examine directly the effects of chronic hyperkalemia on medullary ammonium accumulation and collecting duct ammonium secretion, micropuncture experiments were performed in the inner medulla of Munich-Wistar rats pair fed a control or high-K+ diet for 7-13 d. In situ pH and total ammonia concentrations were measured to calculate NH3 concentrations for base and tip collecting duct and vasa recta. Chronic K+ loading was associated with significant systemic metabolic acidosis and a 40% decrease in urinary ammonium excretion. In control rats, 15% of excreted ammonium was secreted between base and tip collecting duct sites. In contrast, no net transport of ammonium was detected along the collecting duct in high-K+ rats. The decrease in collecting duct ammonium secretion in hyperkalemia was associated with a decrease in the NH3 concentration difference between vasa recta and collecting duct. The fall in the NH3 concentration difference across the collecting duct in high-K+ rats was due entirely to a decrease in [NH3] in the medullary interstitial fluid, with no change in [NH3] in the collecting duct. These results indicate that impaired accumulation of ammonium in the medullary interstitium, secondary to inhibition of ammonium absorption in the medullary thick ascending limb, may play an important role in reducing collecting duct ammonium secretion and urinary ammonium excretion during chronic hyperkalemia.

Original languageEnglish (US)
Pages (from-to)1443-1449
Number of pages7
JournalJournal of Clinical Investigation
Volume90
Issue number4
StatePublished - Oct 1992

Fingerprint

Hyperkalemia
Ammonium Compounds
Rectum
Extremities
Extracellular Fluid
Acidosis
Punctures
Ammonia
Wistar Rats

Keywords

  • Collecting duct acidification
  • Countercurrent multiplication
  • Hyperkalemic metabolic acidosis
  • Loop of henle
  • Urinary ammonia excretion

ASJC Scopus subject areas

  • Medicine(all)

Cite this

Chronic hyperkalemia impairs ammonium transport and accumulation in the inner medulla of the rat. / DuBose, Thomas D.; Good, David.

In: Journal of Clinical Investigation, Vol. 90, No. 4, 10.1992, p. 1443-1449.

Research output: Contribution to journalArticle

@article{91b72950588647269ae8d3844470ff18,
title = "Chronic hyperkalemia impairs ammonium transport and accumulation in the inner medulla of the rat",
abstract = "Previously we demonstrated in rats that chronic hyperkalemia had no effect on ammonium secretion by the proximal tubule in vivo but that high K+ concentrations inhibited ammonium absorption by the medullary thick ascending limb in vitro. These observations suggested that chronic hyperkalemia may reduce urinary ammonium excretion through effects on medullary transport events. To examine directly the effects of chronic hyperkalemia on medullary ammonium accumulation and collecting duct ammonium secretion, micropuncture experiments were performed in the inner medulla of Munich-Wistar rats pair fed a control or high-K+ diet for 7-13 d. In situ pH and total ammonia concentrations were measured to calculate NH3 concentrations for base and tip collecting duct and vasa recta. Chronic K+ loading was associated with significant systemic metabolic acidosis and a 40{\%} decrease in urinary ammonium excretion. In control rats, 15{\%} of excreted ammonium was secreted between base and tip collecting duct sites. In contrast, no net transport of ammonium was detected along the collecting duct in high-K+ rats. The decrease in collecting duct ammonium secretion in hyperkalemia was associated with a decrease in the NH3 concentration difference between vasa recta and collecting duct. The fall in the NH3 concentration difference across the collecting duct in high-K+ rats was due entirely to a decrease in [NH3] in the medullary interstitial fluid, with no change in [NH3] in the collecting duct. These results indicate that impaired accumulation of ammonium in the medullary interstitium, secondary to inhibition of ammonium absorption in the medullary thick ascending limb, may play an important role in reducing collecting duct ammonium secretion and urinary ammonium excretion during chronic hyperkalemia.",
keywords = "Collecting duct acidification, Countercurrent multiplication, Hyperkalemic metabolic acidosis, Loop of henle, Urinary ammonia excretion",
author = "DuBose, {Thomas D.} and David Good",
year = "1992",
month = "10",
language = "English (US)",
volume = "90",
pages = "1443--1449",
journal = "Journal of Clinical Investigation",
issn = "0021-9738",
publisher = "The American Society for Clinical Investigation",
number = "4",

}

TY - JOUR

T1 - Chronic hyperkalemia impairs ammonium transport and accumulation in the inner medulla of the rat

AU - DuBose, Thomas D.

AU - Good, David

PY - 1992/10

Y1 - 1992/10

N2 - Previously we demonstrated in rats that chronic hyperkalemia had no effect on ammonium secretion by the proximal tubule in vivo but that high K+ concentrations inhibited ammonium absorption by the medullary thick ascending limb in vitro. These observations suggested that chronic hyperkalemia may reduce urinary ammonium excretion through effects on medullary transport events. To examine directly the effects of chronic hyperkalemia on medullary ammonium accumulation and collecting duct ammonium secretion, micropuncture experiments were performed in the inner medulla of Munich-Wistar rats pair fed a control or high-K+ diet for 7-13 d. In situ pH and total ammonia concentrations were measured to calculate NH3 concentrations for base and tip collecting duct and vasa recta. Chronic K+ loading was associated with significant systemic metabolic acidosis and a 40% decrease in urinary ammonium excretion. In control rats, 15% of excreted ammonium was secreted between base and tip collecting duct sites. In contrast, no net transport of ammonium was detected along the collecting duct in high-K+ rats. The decrease in collecting duct ammonium secretion in hyperkalemia was associated with a decrease in the NH3 concentration difference between vasa recta and collecting duct. The fall in the NH3 concentration difference across the collecting duct in high-K+ rats was due entirely to a decrease in [NH3] in the medullary interstitial fluid, with no change in [NH3] in the collecting duct. These results indicate that impaired accumulation of ammonium in the medullary interstitium, secondary to inhibition of ammonium absorption in the medullary thick ascending limb, may play an important role in reducing collecting duct ammonium secretion and urinary ammonium excretion during chronic hyperkalemia.

AB - Previously we demonstrated in rats that chronic hyperkalemia had no effect on ammonium secretion by the proximal tubule in vivo but that high K+ concentrations inhibited ammonium absorption by the medullary thick ascending limb in vitro. These observations suggested that chronic hyperkalemia may reduce urinary ammonium excretion through effects on medullary transport events. To examine directly the effects of chronic hyperkalemia on medullary ammonium accumulation and collecting duct ammonium secretion, micropuncture experiments were performed in the inner medulla of Munich-Wistar rats pair fed a control or high-K+ diet for 7-13 d. In situ pH and total ammonia concentrations were measured to calculate NH3 concentrations for base and tip collecting duct and vasa recta. Chronic K+ loading was associated with significant systemic metabolic acidosis and a 40% decrease in urinary ammonium excretion. In control rats, 15% of excreted ammonium was secreted between base and tip collecting duct sites. In contrast, no net transport of ammonium was detected along the collecting duct in high-K+ rats. The decrease in collecting duct ammonium secretion in hyperkalemia was associated with a decrease in the NH3 concentration difference between vasa recta and collecting duct. The fall in the NH3 concentration difference across the collecting duct in high-K+ rats was due entirely to a decrease in [NH3] in the medullary interstitial fluid, with no change in [NH3] in the collecting duct. These results indicate that impaired accumulation of ammonium in the medullary interstitium, secondary to inhibition of ammonium absorption in the medullary thick ascending limb, may play an important role in reducing collecting duct ammonium secretion and urinary ammonium excretion during chronic hyperkalemia.

KW - Collecting duct acidification

KW - Countercurrent multiplication

KW - Hyperkalemic metabolic acidosis

KW - Loop of henle

KW - Urinary ammonia excretion

UR - http://www.scopus.com/inward/record.url?scp=0026469735&partnerID=8YFLogxK

UR - http://www.scopus.com/inward/citedby.url?scp=0026469735&partnerID=8YFLogxK

M3 - Article

VL - 90

SP - 1443

EP - 1449

JO - Journal of Clinical Investigation

JF - Journal of Clinical Investigation

SN - 0021-9738

IS - 4

ER -