L23- Iron Metab & Its Disorders (#5) Flashcards
An average animal contains approx ____ mg of iron per poundi n the body, which is distributed in the following way: ____% for storage, ___% for use
10-20 mg
- 25% for storage, 75% in use
Because animal cells and organism are unable to promote iron loss, the only way iron loss can be achieved is by _____
Bleeding
How is iron homeostasis maintained?
By absorbing an amount of iron equivalent to that which is unwillingly lost daily
Iron content of various foods and feeds can be divided into? (3 things and give mg/kg amounts)
- High iron (>50 mg/kg)
- Intermediate iron (10-50 mg/kg)
- Low iron (
What are examples of high iron foods?
Organ meats, Brewer’s yeast, egg yolks, wheat germ
What are examples of intermediate iron foods?
Muscle meat, fish, most green veggies and cereal
What are examples of low iron foods?
Milk, milk products, and non-green veggies
What are the 3 forms that animal dietary iron exists in?
- Heme iron
- Ferrous iron (non-heme iron)
- Ferric iron (non-heme iron)
The bioavailability of the dietary iron goes in what order?
Heme iron» Fe2+ > Fe3+
Which dietary iron is mainly found in meat and is the most bioavailable form of dietary iron?
Heme iron
_____ iron is the most abundant form of non-heme iron
Ferric iron
What are two drawbacks of ferric iron?
- Insoluble at physiological pH
- Not very bioavailable
Clinical note: Bioavailability is decreased in individuals with achlorhydria- what is this?
Decreased HCl levels from gastric juice
Clinical note: ______ also diminish the iron availability by raising the gastric pH, leading to ferric aggregate formation
Antacids
______ is soluble at physiological pH and is more bioavailable than ferric iron
Ferrous iron
Meal composition can either or diminish _____ iron bioavailability
Non-heme
______________ such as cysteine, sorbitol, and fructose increase iron absorption
Reducing molecules
Vitamin C enhances iron availability in what 2 ways?
- Vit C reduces ferric iron Fe3+ to ferrous Fe2+
2. Vit C, as well as AA and glucose, can form complexes with iron. Iron complexes increase bioavail of ferrous iron
What other two things are enhancers of iron absorption besides reducing molecules?
- AA
- Acidic foods
What are phytates, tannins, and phosphates and phosphoproteins, oxalate, and calium, zinc copper or mangages ions categorized as?
Inhibitors of iron absorption
EXPLAIN. Dietary iron deficiency is rare in adult pets. However, young puppies and kittens are esp vulnerable to iron deficiency. Why?
Nursing animals are more susceptible to this problem because milk is low in iron. Hence, iron is needed for growth exceeds the supply avail from diet and body stores. However, it is very unlikely that iron deficiency would occur in post-weaning animals fed balanced meals
EXPLAIN. In order to inc iron absorp in an iron deficient puppy, is it better to combine or to separate iron supplements and milk?
It would be better to separate them in order to minimize effect of calcium (inhibitor competing with iron) in iron absorption
______ is a serum protein in charge of transporting iron through circulation
Transferrin
What is the difference btwn absorption and uptake?
Absorption: refers to dietary iron moving thru enterocytes into circulation
Uptake: iron from circulation moving into cells in body tissues
Where does iron absorption occur?
At the enterocytes of the duodenum and upper jejunum
Clinical note: Surgical removal of any part of the duodenum and/or upper jejunum will _______ iron absorption
Decrease
Why is unbound iron toxic?*
Because it non-enzymatically catalyzes the formation of highly destructive hydroxyl radical (OH)- this is called the Fenton reaction
Why are hydroxyl radicals so destructive?
They have the potential to damage virtually every cellular component
Transferrin is an abundant serum protein which binds ferric iron with high affinity, thus causing what 3 things?
- Solubilizes iron
- Attenuates iron reactivity
- Delivers iron to sites of use and storage
What is apotransferrin?
When transferrin is NOT bound to iron
When transferrin is bound to one Fe3+ atoms, it is called?
Diferric transferrin
What are transferrin receptors (TfR)?
A plasma membrane protein which binds and mediates the cellular uptake of the iron-transferrin complex
What is another form of ferritin that has been partially modified in lysosomes?
Hemosiderin
What are the 3 involuntary mechanism to lose iron?
- Sloughing off skin and mucosal cells
- Sweat, hair and nail loss
- Bleeding
How much mg of iron does one ml of blood contain?***
0.5 mg of iron!
EXPLAIN AND CALCULATE. A mixed breed dog affected with a bleeding neoplasm is losing 10 ml of blood daily. How long would it take to deplete his iron stores? Assume his initial iron stores are 1,000 mg, average diet and constant blood loss.
- There is 0.5 mL of iron per mL of blood.
- 10 mL blood lost per day (0.5 mg Fe/mL blood * 10 mL= 5 mg Fe lost per day)
- 1000 mg Fe stores/ 5 mg lost per day = 200 days to deplete iron stores!!
What are the 4 lab assessment/tests of iron?
- Serum iron
- TIBC
- % Transferrin saturation
- Serum ferritin
What are the 3 primary cause of iron defeciencies?
- Nutritional
- Inadequate absorption
- Chronic blood loss
Out of the 3 primary causes of iron deficiency, which one would be the most common in small animals?
Chronic blood loss
Treatment of iron deficiency requires _____? (dont overthink)
Iron supplements
Predict the following test results in case of iron deficiency patient (4 tests)
- Serum iron= decreased
- TIBC = increased
- % transferrin saturation = decreased
- Serum ferritin = decreased
In an animal with iron deficiency anemia, the levels of serum ferritin (iron stores) are inversely proportional to __________________ lvls
Serum transferrin lvls
When iron levels are high in an animal with iron deficiency, what things should we take note of?
Make note of if there are changes in: ferritin, transferrin
Ferritin: is high in order to store the iron
Transferrin: is low
In the four tests I want to know whats that all about serum iron, TIBC, % Transferrin saturation, and Serum ferritin. What are the patient results after seeing that iron is unavailable?
Serum iron: dec
TIBC: dec
% Transferrin sat: Dec
Serum ferritin: Incr
In the four tests I want to know whats that all about serum iron, TIBC, % Transferrin saturation, and Serum ferritin. What are the patient results after seeing that iron is unavailable?
Serum iron: inc
TIBC: dec
% Transferrin sat: inc
Serum ferritin: Incr
Serum ferriton (iron stores) are ________ to Tf (TIBC) lvls
Inversely proportional
In a dog with iron overload, what occurs to Ferritin and TIBC (Tf)?
Increased ferritin Decreased TIBC (Tf)
Why is iron so important for animals?
It is an essential micronutrient for all living organisms
