Renin-Angiotensin-Aldosterone System Flashcards
What main structures make up the juxtaglomerular apparatus?
Macula densa
Juxtaglomerular cells (granular cells)
Mesangial cells
What is the macula densa?
Collection of epithelial cells in the distal convoluted tube where it lies adjacent to the glomerulus
What is the role of the macula densa?
Senses [NaCl] in DCT
- if increased => secretes adenosine and inhibits NO which causes vasoconstriction of afferent arteriole
- if decreased => secrete prostaglandins which act on granular cells to increase renin secretion
What are juxtaglomerular cells?
Collection of cells surrounding the afferent arteriole adjacent to the macula densa
What is the role of juxtaglomerular cells?
Secrete renin in response to:
- decreased afferent arteriole pressure
- decreased NaCl in DCT
- beta-1 adrenergic stimulation
What are mesangial cells?
Smooth muscle cells within the glomerulus
What is the function of mesangial cells?
Contract in response to sympathetic discharge due to decreased GFR
What are the three major mechanisms for autoregulation of GFR?
Myogenic response
- causes vasoconstriction in response to increased BP
Adenosine and NO
RAA system
What is the effect of angiotensin II?
Constricts both afferent and efferent arteriole, but efferent arteriole effect is more marked since smaller diameter
- Th. increased efferent pressure, and increased GFR
Increased sympathetic activity
Increased tubular reabsorption of salt and water
Increased aldosterone secretion
Increased ADH secretion
Prevents excessive vasoconstriction by triggering prostalglandin release
What are the effects of unilateral renal artery stenosis?
Refractory hypertension
- affected kidney causes increased renin due to hypoperfusion => increased systemic BP
Normal renal function - to- mild renal impirment
- renal function copes since one kidney affected
What are the effects of bilateral renal artery stenosis?
Refractory hypertension
- pulmonary oedema may result
Significant renal impairment
Acute detorioration in renal function with ACE-Is
Name some drugs that affect angiotensin and renin
ACE inhibitors - e.g. Ramipril
Angiotensin receptor blockers - e.g. Losartan
Renin inhibitor - aliskiren (used in combination only)
What is the effect of Spironolactone?
Aldosterone antagonist = diuretic (K+ sparing)
What effect do NSAIDs have on afferent and efferent arterioles?
Increased vasoconstriction of afferent arteriole
- due to inhibition of COX enzymes leading to less production of prostaglandins
- prostaglandins cause afferent vasodilation
What effect do Ca2+ channel blockers have on afferent and efferent arterioles?
Inhibit vasoconstriction of afferent and efferent arterioles
