Effect of cortical-medullary gradient for ammonia on urinary excretion of ammonia

Stern, Leonard; Backman, Karen A.; Hayslett, John P.
April 1985
Kidney International;Apr1985, Vol. 27 Issue 4, p652
Academic Journal
Previous studies suggested that a portion of ammonia secreted into the proximal tubule may diffuse directly from Henle's loop into the medullary collecting duct. Since water is absorbed along the course of the descending portion of the loop, it was proposed that the concentration of ammonia increased in loop fluid, and that rapid diffusibility of the free base would facilitate the delivery of ammonia into medullary interstitium where a high level could be maintained by the countercurrent exchange process. In this schema it was proposed that there was an ammonia concentration gradient between medullary structures and cortex, and recovery of ammonia by the medullary collecting duct due to the low pH in tubule fluid at that site. The present study was designed lo evaluate this hypothesis by estimating ammonia concentrations in medullary and cortical tissue, and by correlating medullary levels with secretion rate into the inner medullary collecting duct. In control animals the concentration of total ammonia (NH4+ + NH3+) in inner medullary vasa recta was 9.2 ± 1.5 μmoles/ml, a level 100-fold higher than the cortical level of 0.10 ± 0.01. During acute acidosis the medullary level rose to 22.5 ± 2.7 μmoles/ml, but in acute acidosis during mannitol infusion the level fell to 8.0 ± 1.2. The rate of ammonia secretion into inner medullary collecting duct fluid correlated directly with medullary vasa recta ammonia concentration. These data provide evidence for a steep ammonia concentration gradient between the medulla and cortex, and suggest that the diffusion gradient across collecting duct epithelium governs the rate of the addition of ammonia to collecting duct fluid.


Related Articles

  • The acid-activated signaling pathway: Starting with Pyk2 and ending with increased NHE3 activity. Preisig, P. A. // Kidney International;Dec2007, Vol. 72 Issue 11, p1324 

    On a typical Western diet, the body is faced with the generation of a metabolically derived acid load that must be excreted to maintain systemic acid–base balance. The kidney is responsible for this task and matches daily acid excretion with daily acid production. Multiple nephron...

  • Adaptive change in ammonia excretion in renal insufficiency. MacLean, Alan J.; Hayslett, John P. // Kidney International;May1980, Vol. 17 Issue 5, p595 

    Experiments were performed to study the mechanism of the compensatory increase in the excretion of metabolic acid by residual nephrons after reduction in renal mass. Despite a decrease in nephron population to 20% of control, total excretion of acid remained similar to pair-fed controls due to...

  • Functional characterization of nonsynonymous single nucleotide polymorphisms in the electrogenic Na-HCO cotransporter NBCe1A. Yamazaki, Osamu; Yamada, Hideomi; Suzuki, Masashi; Horita, Shoko; Shirai, Ayumi; Nakamura, Motonobu; Seki, George; Fujita, Toshiro // Pflugers Archiv European Journal of Physiology;Feb2011, Vol. 461 Issue 2, p249 

    The electrogenic Na-HCO cotransporter NBCe1 encoded by SLC4A4 plays essential roles in the regulation of intracellular/extracellular pH. Homozygous mutations in NBCe1 cause proximal renal tubular acidosis associated with ocular abnormalities. In the present study, we tried to perform functional...

  • Effects of nephron reduction and dietary protein content on renal ammoniagenesis in the rat. Schoolwerth, Anton C.; Sandler, Richard S.; Hoffman, Patricia M.; Klahr, Saulo // Kidney International;Jan1975, Vol. 7 Issue 1, p397 

    Urinary ammonium excretion, in vitro ammoniagenesis and the activities of renal cortical phosphate-dependent glutaminase (PDG) and glutamic dehydrogenase (GLDH) were measured in rats with a reduced renal mass. Following contralateral nephrectomy, ammonium excretion per nephron, ammonia...

  • Citrate Excretion in Renal Tubular Acidosis. Morrissey, James F.; Ochoa Jr., Manuel; Lotspeich, William D.; Waterhouse, Christine // Annals of Internal Medicine;Jan63, Vol. 58 Issue 1, p159 

    Studies urinary citrate excretion under varying conditions in a patient with documented renal tubular acidosis. Case history; Lack of relation between defective citrate excretion and potassium depletion; Effect of large doses of alkalinizing substances in the patient.

  • SDF1 induction by acidosis from principal cells regulates intercalated cell subtype distribution. Schwartz, George J.; XiaoBo Gao; Shuichi Tsuruoka; Purkerson, Jeffrey M.; Hu Peng; D'Agati, Vivette; Picard, Nicolas; Eladari, Dominique; Al-Awqati, Qais; Gao, XiaoBo; Tsuruoka, Shuichi; Peng, Hu // Journal of Clinical Investigation;12/1/2015, Vol. 125 Issue 12, p4365 

    The nephron cortical collecting duct (CCD) is composed of principal cells, which mediate Na, K, and water transport, and intercalated cells (ICs), which are specialized for acid-base transport. There are two canonical IC forms: acid-secreting α-ICs and HCO3-secreting β-ICs. Chronic...

  • Structural adaptation in initial collecting tubule following reduction in renal mass. Zalups, Rudolfs K.; Stanton, Bruce A.; Wade, James B.; Giebisch, Gerhard // Kidney International;Apr1985, Vol. 27 Issue 4, p636 

    Tubular function studies have shown that nephrectomy leads to a sharp increase in potassium secretion by initial collecting tubules. The aim of this study was to examine the relationship between potassium transport and the cellular morphology of the distal nephron. Clearance and ultrastructural...

  • Segmental characterization of defects in collecting tubule acidification. Batlle, Daniel C. // Kidney International;Oct1986, Vol. 30 Issue 4, p546 

    The aim of this study was to investigate conical collecting tubule (CCT) function in normal individuals and in patients with distal renal tubular acidosis (DRTA) using furosemide (80 mg orally) as a tool to stimulate H+ and K+ secretion by enhancing Na delivery and transport in this nephron...

  • Nitrogen recovery by urea hydrolysis and struvite precipitation from anthropogenic urine. Kabdaşlı, I.; Tünay, O.; İşlek, Ç.; Erdinç, E.; Hüskalar, S.; Tatlı, M. B. // Water Science & Technology;2006, Vol. 53 Issue 12, p305 

    Human urine is a source of nutrients and has a significant potential for recycle of nitrogen. Recently, much research focused on separate collection and treatment of human urine. Recovery of nutrients from human urine requires hydrolysis of urea into ammonia and subsequent removal of ammonia and...


Read the Article


Sorry, but this item is not currently available from your library.

Try another library?
Sign out of this library

Other Topics