9.4 Renal Blood Flow Autoregulation

Question 1

List two mechanisms of glomerular blood flow autoregulation

Answer 1

• Glomerular/afferent/efferent arterioles have adrenaline and noradrenaline receptors, meaning they constrict w/ sympathetic activity. Afferent is less sensitive than efferent to this (why?)
• Tubuloglomerular feedback: macula densa detects sodium as a proxy for BP, causing corresponding dilation/constriction of arteries

Question 2

Explain two substances which that are released by the JGA (and why they’re released), and how this contributes to glomerular autoregulation

Answer 2

• In response to low sodium at the macula densa, the JG cells release renin. This not only acts to increase BP through aldosterone, but angiotensin itself also vascoconstricts the EFFERENT arteriole, increasing net filtration pressure and thus GFR
• In response to low sodium, JG cells also release prostaglandins that dilate the AFFERENT arteriole (can you think of a drug that might inhibit this?)

Question 3

List 5 factors that can decrease renal autoregulation (and why)

Answer 3

1. Chronic hypertension (damages vasculature)
2. Diabetes (diabetic nephropathy due to hyperglycaemia)
3. Chronic renal disease (scarring of nephrons)
4. Ageing (less compliant vasculature)
5. Medications (e.g. ACEis, ARBs, NSAIDs)