Regulation Of Renal Blood Flow
REGULATION OF RENAL BLOOD FLOW
DETERMINANTS OF RENAL BLOOD FLOW:
- Pressure gradient across renal vasculature.
- Renal arterial & venous pressure.
- Total renal vascular resistance.
- Controlled by sympathetic nervous system.
- Local hormones.
- Intrinsic control mechanism.
- Oxygen consumption.
REGULATION OF RENAL BLOOD FLOW:
1. RENAL AUTOREGULATION:
- Property of renal blood flow of being independent of mean systemic arterial pressure referred “Autoregulation”.
- Involves adjustments in afferent glomerular arteriole resistance.
Acts via two processes:
- Myogenic control of afferent arteriole.
- Distal Tubule-glomerular feedback.
Importance of autoregulation:
- Maintain relatively constant GRF levels.
- Precise control of renal water & solutes excretion.
- Maintenence of oxygen & nutrient normal delivery.
- Removal of metabolic waste.
Type I – Myogenic autoregulation:
- Maintains renal blood flow as well as GRF.
- Occurs in denervated, isolated, perfused kidneys.
- Produced by direct contractile response to smooth muscle stretch of afferent arteriole.
- Nitric oxide involved.
Clinical significance:
- Important in protecting kidney from hypertension-induced injury.
- Steps:
- Sudden rise of BP → Myogenic constrictor response in afferent arterioles → activated within seconds → attenuates transmission of increased arterial pressure to glomerular capillaries.
Type II – Tubuloglomerular feedback:
- Mediates renal vasoconstriction
- In response to increased sodium chloride delivery to macula densa.
2. RENAL VASOCONSTRICTION:
Norepinephrine (noradrenaline)-
- Acts on interlobular arteries & afferent arterioles.
Angiotensin II-
- Powerful renal vasoconstrictor
- Preferably acts on efferent arterioles.
Endothelin
3. RENAL VASODILATION:
- Prostaglandins & bradykinins
- PGE1 & PGE2 mainly.
- Acts against sympathetic nerves & angiotensin II
- Opposes afferent arteriole vasoconstriction caused by them
Endothelial-derived nitric oxide –
- Decreases renal vascular resistance
Dopamine –
- Secreted intrinsically by kidney
- Causes renal vasodilation & natriuresis.
Acetylcholine
4. OTHERS:
Diet:
- High-protein & glucogenic diet raises renal blood flow & GRF
Exam Question
REGULATION OF RENAL BLOOD FLOW:
RENAL AUTOREGULATION:
Type I – Myogenic autoregulation:
- Maintains renal blood flow as well as GRF.
- Produced by direct contractile response to smooth muscle stretch of afferent arteriole.
Type II – Tubuloglomerular feedback–mediated renal vasoconstriction
RENAL VASODILATION:
- Prostaglandins & bradykinins
- PGE1 & PGE2 mainly.
Don’t Forget to Solve all the previous Year Question asked on Regulation Of Renal Blood Flow