As part of the so-called renin-angiotensin-aldosterone system (RAAS), angiotensin 2 exerts a considerable influence on the maintenance of many processes within the organism. Angiotensin 2 is a hormone produced by the body itself and belongs to the group of peptide hormones (proteohormones). All peptide hormones have in common that they are composed of small individual components, the amino acids, and that they can be easily dissolved in an aqueous environment.
This means that all proteohormones are water-soluble (hydrophilic/lipophobic). Angiotensin 2 consists of a total of eight amino acids, two of which must be taken up in sufficient quantities with food (essential amino acids). Due to its water-soluble property, angiotensin 2 is not able to pass through the cell membrane by diffusion.
The tissue hormone can only unfold its messenger function after binding to a suitable surface receptor and exert an influence on organic cells. As a component of the renin-angiotensin-aldosterone system, angiotensin 2 plays a decisive role in the regulation of
- Water balance
- Maintenance of kidney function and
- Blood pressure
The activation of the renin-angiotensin-aldosterone system and thus also the formation of angiotensin 2 is triggered in the body by special sensors in the kidney area. The kidneys react to falling blood pressure or reduced tissue perfusion by releasing the enzyme renin.
Renin is an enzyme that is able to split off the precursor hormone angiotensionogen, angiotensin 1, which is produced in the liver cells. Angiotensin 1 is the direct precursor of the active tissue hormone angiotensin 2. The conversion of the hormone precursor to the active hormone is done with the help of the so-called angiotensin converting enzyme (ACE).
The renin-angiotensin-aldosterone system and its intermediate product angiotensin 2, are significantly involved in the regulation of blood pressure and blood volume in the organism. The most important task of this regulatory system is above all to compensate for large losses of volume and drops in blood pressure. In an organism with stable circulation and volume, the renin-angiotensin-aldosterone system is normally inactivated and the formation of angiotensin 2 is suppressed.
Only when there is an acute drop in blood pressure, which is registered by special kidney cells, does the body stimulate the formation of angiotensin 2. Over several steps, angiotensin 2 is released from its precursor molecules and transported via the bloodstream. Due to its water-soluble properties, however, the hormone is not able to freely pass through the cell membrane into its target cells.
For angiotensin 2 to be effective, it must bind to a specific receptor on the cell surface (AT receptor). This surface receptor is mainly found on the cell membrane of blood vessel, kidney and adrenal cells. After angiotensin 2 has bound to the AT receptor of smooth muscle cells, an activation cascade is triggered inside the target cell, which ultimately leads to the contraction (tension) of the smooth vascular muscle cells.
In this way, the previously dropped blood pressure is raised again through the influence of the renin-angiotensin-aldosterone system and the contraction (tension) of the vascular muscle cells. In the kidney area, the activation of the specific angiotensin 2 receptor has a particular effect on the smallest renal vessels. The smooth vascular muscle cells of the kidney also react to the stimulus triggered by angiotensin 2 with a contraction.
With the help of this process, despite a drop in blood pressure, an even blood supply to the kidney can be ensured and thus an almost constant kidney function. In addition, the concentration of the tissue hormone angiotensin 2 also affects the adrenal glands. There, however, angiotensin 2 has no direct effect on the vessels and vascular muscle cells.
The effect of the hormone is rather mediated indirectly in this organ by stimulating the release of other messenger substances (aldosterone and adrenaline). In the pituitary gland (hypophysis), too, increased release of further hormones is stimulated after angiotensin 2 has bound to the specific cell surface receptor. The effect of angiotensin 2 on the blood circulation and the individual organ systems is therefore far-reaching.
For this very reason, the renin-angiotensin-aldosterone system and the hormone angiotensin 2 represent important targets for the pharmaceutical industry in the treatment of hypertension. The common drugs that target the renin-angiotensin-aldosterone system are generally used to reduce high blood pressure (hypertension). These drugs are so-called antihypertensives. In addition to inhibiting the synthesis of angiotensin 2, which ultimately results in the suppression of the hormone-specific effect, it is also possible to intervene at the level of renin. The most relevant side effects of antihypertensives include
- Chronic chesty cough
- Tiredness and
- Circulatory problems
- Main page: Angiotensin 2
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- Angiotensin-2 antagonists
- ACE inhibitors
- ACE inhibitors Side effects