Pharmacology for Anaesthesia and Intensive Care

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16 Antihypertensives

Liver

Lungs

Kidney

Angiotensinogen

Angiotensin I

Renin

Angiotensin II

Angiotensin III

Inactive metabolites

Angiotensin receptor

Aldosterone

Bradykinin

ACE

Inactive fragments

Figure 16.1.Renin–angiotensin–aldosterone system. ,Enzyme action; —–•,negative

feedback.

Angiotensin II

Mechanism of action

Twosubtypes of angiotensin II receptor exist, AT 1 and AT 2 .Angiotensin has a greater

affinity for AT 1 receptors, which are G-protein-coupled.

Effects


Potent vasoconstriction (about five times as potent as noradrenaline). Directly on

arterioles and indirectly via central mechanisms.


Blockade of noradrenaline re-uptake (uptake 1) at sympathetic nerves and sym-

pathetic nervous system activation.


Central effects – it increases thirst and the release of ADH and ACTH.


Itstimulates the release of aldosterone from the adrenal cortex and inhibits the

release of renin from the juxtaglomerular cells.


Reduced glomerular filtration rate.