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Bio-bullets

What lies behind the kidney’s iron curtain?

Despite its rusty colour, urine is revealingly rust-free.

professor caricatureProf. Mumblebard claims: “A main function of the human kidney is to excrete toxic substances including any excesses of heavy metals absorbed into the body. However, in the case of iron, urinary excretion can be too slow because{njaccess 2, 3, 4, 5, 6, 7, 8} haemoglobin – which contains most of the body’s iron – is packed into red blood cells that are far too large to pass through the membrane separating the blood from the tubules of the kidney. Because iron is contained in protein molecular complexes, bleeding is sometimes required to treat patients suffering from excess iron in their tissues.”{!njaccess}… See the hidden half of Prof. Mumblebard’s claim by subscribing here{/njaccess}

logoRobin and the Honey Badger respond: “Iron is in a different category from all the other metallic elements in the human body in that its excretion via the kidney is negligible. This strict barring of iron from the renal tubules is anomalous because various iron-containing molecules in the blood plasma are known – at least in other mammals – to penetrate the renal filter. Despite the potential permeability of the kidney to iron, the chemistry of urine shows{njaccess 2, 3, 4, 5, 6, 7, 8} that all ionic and molecular forms of iron are blocked, either by chemical discrimination at the renal filter or by prompt retrieval into the blood of any iron that does pass into the renal tubules. The significance of the particular prohibition of iron is that it divulges the real dedication of the kidney: not excretion but instead the precarious balancing of ionic charges across the chemical spectrum throughout the circulatory system. To achieve such balancing – which includes optimising the full regime of oxidant, anti-oxidant, and acid-base reactions in all organs of the body – the kidney excludes both oxygen and iron. Oxygen has such an affinity for electrons that it can unravel organic molecules, and the ferrous form of iron – which would prevail under the anoxic conditions in the renal tubules if iron were to enter the kidney – is also a dangerous ‘free radical’ in its own right. What distinguishes iron from other metals is that it is inherently so unstable and reactive that its prevalence in the blood must be balanced by its minimisation in the renal filtrate. The overall effect of the exclusion of both oxygen and iron from the renal tubules is that the positive and negative charges – at scales from electron and proton to extremely complex ions – can be equilibrated and ‘free radical’ activity can continually be optimised throughout the human body.” {!njaccess}… Reveal the hidden half of this response by Robin and the Honey Badger by subscribing here{/njaccess}

Please join us here at the Bio-edge with your own comments. In the discussion below we encourage links to any evidence supporting either Prof. Mumblebard or Robin and the Honey Badger. Illustrations are welcome but please cite all sources or we may be forced under copyright to delete your comment.

 

Last modified on 17 July 2015

Comments   

0 #1 Julien Peter Benney 2014-08-20 15:26
This is an interesting insight.

Ferrous iron is highly stable in the absence of oxygen – it is a weaker reducing agent than iodide ion – but i had no idea that ferrous iron would be dangerous as a free radical analogous to powerfully oxidising superoxides.

Metal ions that ferrous ion would reduce are highly siderophile and much too rare in the crust to be biologically useful, so the question is what molecules ferrous iron would attack and what would be formed??
0 #2 Freerad 2014-08-21 08:36
Anthony Colpo dedicates a chapter to the problem of iron overloading in his book “The Great Cholesterol Con”. There appears to be some evidence that overall mortality in middle-aged men is positively correlated with ferritin in the blood. I wonder if this is related to the fact that the kidney can’t get rid of iron easily…?
0 #3 Taklamakan 2014-08-22 08:35
@Freerad. It is strange that the human body can’t get rid of iron. But iron overloading is probably more about the rate of intake of iron from the small intestine being too fast for some reason. After all, that is how the body has balanced its iron for millions of years…Possible reasons for the problem are malfunctioning intestinal epithelial cells; the malfunctioning could be as a result of too many processed carbohydrates in the modern diet.
0 #4 gena count 2014-08-22 11:41
A gene mutation (on chromosome 6) is an autosomal disorder found most commonly in peoples of a Northern European descent and which is associated with the condition of haemochromatosi s which disrupts iron metabolism in the body and an overload results. As far as I know, venepuncture, sometimes weekly is the only treatment. Interesting that the kidney plays no part in the excretion of this excess iron.
0 #5 Grant M 2014-08-27 08:46
The sedentary nature of modern humans may also play a role. Exercise apparently can lead to increased rates of intestinal bleeding from very small exercise-induce d injuries in the gut. That can be good because it allows some of the excess Fe to be lost.
0 #6 Taklamakan 2014-10-06 08:31
@Julien. Ferrous iron - according to soil chemists - is a strong reducing agent in soils. Is there any reason why this would not apply to the renal tubules in kidneys? Please do point me to your list of reducing agents.

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