Afferent arteriole and juxtaglomerular cells
Glomerulus · Renin Myogenic PGE2 dilates
Terminal branch of the interlobular (cortical radial) artery that delivers blood to the glomerular capillary tuft; its wall holds the renin-secreting juxtaglomerular (granular) cells. Its tone sets glomerular capillary pressure and therefore GFR.
Detail
- Supplies
- Glomerular capillaries; renal blood flow ~1.1-1.2 L/min (20-25% of cardiac output), renal plasma flow ~600 mL/min
- Autoregulation
- Myogenic stretch response plus tubuloglomerular feedback hold renal blood flow and GFR near-constant across MAP ~80-180 mmHg
- Dilators
- Prostaglandins PGE2/PGI2, nitric oxide, ANP, low macula densa NaCl delivery
- Constrictors
- Adenosine (A1) from the macula densa, sympathetic alpha-1, endothelin, angiotensin II (weaker here than on the efferent)
- Secretes
- Renin from JG cells in response to low afferent pressure (intrarenal baroreceptor), low macula densa NaCl delivery, and beta-1 adrenergic stimulation
When it goes wrong
NSAID in a dehydrated, cirrhotic or heart-failure patient (prostaglandin-dependent afferent dilatation lost)
Afferent constriction, GFR falls, pre-renal acute kidney injury; with an ACE inhibitor and a diuretic this is the 'triple whammy'
Renal artery stenosis lowering afferent pressure
Sustained renin release and secondary hyperaldosteronism: hypertension with hypokalaemia and high renin
Beta-blocker
Reduced renin release (part of the antihypertensive effect); adds to hyperkalaemia risk when combined with other RAAS blockers
Practise this structure
1 question in the bank tagged Glomerular Filtration.