Outline the physiology of, and factors which regulate levels of angiotensin.
For a good answer it was expected that candidates would mention the relationship of
angiotensinogen, angiotensin I, renin and Angiotensin Converting Enzyme to angiotensin II
production, the actions and fate of angiotensin II and factors that regulate angiotensin II. It
was expected that candidates mention angiotensin acts as a potent vasoconstrictor, stimulates
aldosterone secretion, facilitates noradrenaline release, preferentially vasoconstricts Efferent
arteriole in nephron, preserving GFR in low perfusion states, increases renal tubular Na+
reabsorption and increases secretion of vasopressin and ACTH.
Regulation of Angiotensin could be separated into factors increasing angiotensin levels (eg
prostaglandins, low K+ levels, Sympathetic stimulation, decreased Na+ delivery at distal
tubule, any factor contributing to reduced renal blood flow (eg hyovolaemia, cardiac failure,
renal artery stenosis) and factors reducing angiotensin levels (eg hypervolaemia, afferent
arteriolar dilatation and vasopressin).
Syllabus - N1 (h), C2b (f)
Reference: Textbook of medical Physiology, Guyton, Chp 26, Goodman and Gillman, Chp
In brief, the stimuli and enzymatic steps which produce angotensin II:
Or, in the form of words:
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