The Production of Erythrocytes: part B

1.

For the production of red blood cells, next to the usual mixture of amino acids etc, there are three vital components required.

2.

These can only be obtained from the food that is ingested. If the diet is not balanced (typically not enough vegetables such as in junk food), a shortage of any of these compounds may occur which can lead to a shortage of erythrocytes (=anaemia).

3.

The following three compounds are absolutely necessary:
a. Folic Acid: this is required for the duplication of DNA during the replication of stem cells and their differentiation into erythrocytes.
b. Vitamin B12: also required for DNA formation

1.

Folic acid is obtained from food (green vegetables etc) in the small intestine. It is absorbed in the small intestine and stored in the liver.

2.

There can be a shortage of folic acid when there is a chronic intestinal disease or a higher demand of folic acid, especially during pregnancies. Folic acid is then often given to the mother as a supplement.

1.

Vitamin B12 is also absorbed from ‘healthy” food in the small intestine

2.

To protect the vitamin B12 from the acid juices in the stomach, it is bound, in the stomach, to a carrier. This carrier is called “intrinsic factor”.

3.

If there is no or not enough intrinsic factor, then not enough vitamin B12 is absorbed. This will lead to an anemia.

4.

Because the intrinsic factor is made in the mucosa of the stomach, all diseases in which the stomach mucosa is destroyed or missing will cause lack of intrinsic factor and no absorption of vitamin B12.

5.

Such stomach diseases can be a removal of the stomach by surgery (for example to remove a stomach cancer) or a destruction of the mucosa by a toxic fluid (too much alcohol) but also an infection can affect the gastric (=stomach) mucosa.

6.

Normally, most of the vitamin B12 is stored in the liver. In fact, there is so much normally stored that it takes 3-6 months after removing the stomach before symptoms of an anaemia starts to occur.

1.

Fe (=iron) is also obtained from healthy food (and meat).

2.

It is absorbed, in the small intestine, with the help of a transporter called apotransferrin (apo = precursor; trans = transport; ferrin = iron).

3.

When it is coupled to apotransferrin, the complex (iron + apotransferrin) is called: transferrin.

4.

This transferrin circulates, in the blood, to all tissues in the body but mostly to the liver.

5.

Once it arrives to a cell (usually the liver cell), it is decoupled from apotransferrin, passes through the cell membrane, and couples with a special carrier inside the cell. This second, intracellular carrier is called apoferritin. The reaction is similar: apoferritin + Fe = ferritin.

6.

Both ferritin (which is intracellular) and transferrin (which is extracellular) are reversible. This means, when there is a need for iron, that iron is removed from ferritin, goes out of the cell, and is transported as transferrin to the bone marrow, where it is used for the production of erythrocytes.

7.

When there is a shortage of ferritin (which means a shortage of iron stored in the body), then less erythrocytes will be made (=anaemia). This can occur with poor diet or when there is an increased need for iron and erythrocytes, such as during pregnancies.

8.

Some people will take iron supplement, even if they don’t need it. In that case, there could be too much iron inside the body. This can be dangerous. As you saw in 5), iron is stored inside cells as ferritin. If there is not enough apoferritin to store additional iron, then the iron will arrive into the cell but is not attached to apoferritin. Then the iron will crystallize.

9.

These iron crystals are very toxic for the cells, may damage easily the cell membranes and are irreversible. They can no longer be made solvent and used again. These iron crystals are called hemosiderin.

10.

If you have to much hemosiderin, the function of your tissues will decline. For example, if this occurs in the eye, you may become blind. It all depends where the hemosidirin is stored

How does haemoglobin look like anyway?