As part of the so-called renin-angiotensin-aldosterone system (RAAS for short) angiotensin 2 exerts a significant influence on the maintenance of many processes within the organism. Angiotensin 2 is a hormone produced by the body, which 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 can be solved well 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 ingested in sufficient quantities through the diet (essential amino acids).
Due to the water-soluble property, angiotensin 2 is unable to reach the cell membrane via diffusion. The tissue hormone can develop its messenger function only after binding to a suitable surface receptor and exert an influence on organic cells.
As part of the renin-angiotensin-aldosterone system, angiotensin 2 plays a crucial role in the regulation of
The activation of the renin-angiotensin-aldosterone system and thus the formation of angiotensin 2 is triggered in the body by special sensors in the kidneys. The kidneys respond to a drop in blood pressure or decreased tissue perfusion with the release of the enzyme renin.
As an enzyme, renin is able to cleave angiotensin, angiotensin 1, from the precursor hormone formed in the liver cells. Angiotensin 1 represents the direct precursor of the active tissue hormone angiotensin 2. The conversion of the hormone precursor to the active hormone occurs with the help of the so-called angiotensin converting enzyme (ACE for short).
The renin-angiotensin-aldosterone system and its intermediate angiotensin 2, are involved in the organism in the regulation of blood pressure and blood volume.
The most important task of this regulatory system is above all in the compensation of large volume losses and blood pressure drops. In a circulatory and volume stable organism, the renin-angiotensin-aldosterone system is usually inactivated and the formation of angiotensin 2 is suppressed.
Only when an acute drop in blood pressure is detected by special kidney cells, the body stimulates the formation of angiotensin 2. Through 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 pass freely across 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 can be found mainly on the cell membranes of blood vessel, kidney and adrenal cells.
Following the binding of angiotensin 2 to the AT receptor of smooth muscle cells, an activation cascade is triggered inside the target cell, which ultimately results in the contraction (contraction) of vascular smooth muscle cells. In this way, the previously dropped blood pressure is increased again by the influence of the renin-angiotensin-aldosterone system and the tension of the vascular muscle cells.
In the kidney area, activation of the specific angiotensin 2 receptor has an effect on the smallest renal vessels. Kidney smooth muscle cells also respond to the angiotensin 2-triggered stimulus with contraction. With the help of this process, despite decreasing blood pressure a uniform kidney circulation and thus a nearly constant kidney function can be guaranteed.
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 mediated indirectly in this organ, by stimulating the release of other messengers (aldosterone and adrenaline).
Also in the pituitary gland ( pituitary ) is stimulated after binding of angiotensin 2 to the specific cell surface receptor increased release of other hormones. The effect of angiotensin 2 on the blood circulation and the individual organ systems is therefore far-reaching. Precisely for this reason, the renin-angiotensin-aldosterone system and the hormone angiotensin 2 represent important targets for the treatment of hypertension in the pharmaceutical industry.
Common drugs used in the renin-angiotensin-aldosterone system are generally used to lower high blood pressure ( hypertension ). These medicines are so-called antihypertensive drugs. In addition to an inhibition of angiotensin 2 synthesis, which ultimately manifests itself by a suppression of the hormone-specific effect, can also be intervened at the level of renin.
The most relevant side effects of antihypertensive drugs include: