Date:   1/17/2009 8:14:51 PM ( 15 y ago)
Hits:   2,152
URL:   https://www.curezone.org/forums/fm.asp?i=1337917

Hi refreshed

Happy new year to you and everybody and good health to all. With good health everything else is possible!


About that reference to the pH 4.5 lower limit, sorry, I don't recall precisely where I read it. If I had, I would have put a link to it.

This was before I discovered the Ask moreless forum. I was searching about pH, gout and sodium bicarbonate and I found a “scientific” research on the web. The lower limit has to do with the kidneys and how they help regulate the pH.

But here's another link below.

Cheers to all

Will I Ever Learn

http://www.anaesthetist.com/icu/elec/nagacid.htm

Introduction
The confusion in the literature about this topic reflects our ignorance about the normal physiology of pH regulation in the kidney. The body's main long-term defence mechanisms against metabolic acidosis reside in the kidney. Conditions where production or ingestion of vast amounts of acidic substances (for example, salicylate ingestion or diabetic ketoacidosis) compromise this mechanism will generally present with a high anion gap and a normal serum chloride. Conversely, if the anion gap is normal and the serum chloride is raised, then acidosis is likely to be due to compromise of the renal defence mechanism itself. Such acidosis may on occasion be due to an overwhelming stress on the kidney (for example, ongoing massive intestinal bicarbonate loss) but is far more likely to be related to impairment of the renal mechanisms themselves.

Normal pH regulation in the kidney
Where does acid normally come from?
A major source of hydrogen ions is the metabolism of sulphur-containing amino acids, and phosphorylated moieties such as phosphoserine. This is normally in the order of 50 mEq/day. Production of carbonic acid from CO2 made during aerobic respiration is not normally a substantial source, as the CO2 is excreted via the lungs. Other potential sources of acid are organic acids either produced or ingested. These will be considered when we discuss acidosis with an elevated anion gap.
How does the kidney get rid of acid (H+ ions)?
The kidney has several mechanisms of acidifying the urine. Acidification of the urine occurs in both proximal and distal tubules:

* Proximal tubule: More acid is secreted here than in the distal tubule, using an antiport mechanism: sodium ions are absorbed from the lumen of the tubule and hydrogen ions are secreted into the lumen in exchange. Where do the hydrogen ions come from? From the dissociation of carbonic acid into HCO3- and hydrogen ion! The net effect of all this is most beneficial to the organism - precious sodium and bicarbonate ions are retained, in exchange for the excretion of unwanted hydrogen ions. (A tiny amount of hydrogen ion may be secreted into the proximal tubule by other mechanisms).

* Distal tubule & collecting duct: The mechanism in the distal tubule is quite different - although quantitatively smaller, it allows the organism to "fine-tune" urinary pH. Loss of the mechanism results in difficulty acidifying the urine substantially. The main method of distal tubular acidification is using a hydrogen ion pump, driven by ATP. This pump may be similar to the proton pump in the stomach. (There is some evidence that there may also be an electroneutral H+/K+ antiporter working in the distal tubule).

The minimum urinary pH that the kidney can achieve is about 4.5. Although this is about a thousand times more hydrogen ion than is normally present in blood (a pH of 7.4 corresponds to a hydrogen ion concentration of about 4 * 10-8, 4.5 to about 3 * 10-5), as total quantities go, this is a trivial amount of acid. The kidney needs a better way of getting rid of hydrogen ions.



 

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