1. Regulation of Tubular Reabsorption
Kidney lecture 14
The Body Fluids and Kidneys
Lecture 14
Urine Formation II
Regulation of Tubular Reabsorption
Dr. Rashid Mahmood

3. Regulation of Tubular Reabsorption
Kidney lecture 14
Regulation of Tubular Reabsorption
Dr. Rashid Mahmood

4. Reabsorption=124 ml/min Reabsorption= Kf × Net Reabsorptive Force
Kf = Capillary Co-Efficient
= Permeability × Surface Area

5. Reabsorptive Force

6. Regulation of Peritubular Capillary Physical Forces
Arterial Pressure:
↑ BP : ↓ Reabsorption ( ↑ Pc )
2. Resistance of Afferent & Efferent Arterioles:
↑ Resistance: ↓ Pc : ↑ Reabsorption
3. Systemic Colloid Osmotic Pressure:
↑ π c: ↑ Reabsorption
4. Filtration Fraction:
↑ π c: Reabsorption

7. Forces that increase/decrease peritubular capillary reabsorption also increases/decreases reabsorption from renal tubules

9. Pressure Diuresis Pressure Natriuresis
↑ BP → ↑ GFR
↑ BP → ↑ Pc →↓ Reabsorption
↓ Angiotensin-II

10. Hormonal Control of Tubular Reabsorption

11. HORMONES THAT REGULATE ABSORPTION
EFFECTS
Aldosterone
↑ NaCl,H2 O reabsorption, ↑ K+ secretion
Angiotensin -II
↑ NaCl,H2 O reabsorption, ↑H+ secretion
Antidiuretic Hormone
↑H2 O reabsorption
Atrial Natriuretic Peptide
↓ NaCl reabsorption
Parathyroid Hormone
↓ Phosphate Reabsorption ,
↑ Ca++ Reabsorption

12. Angiotensin-II ↑ Aldosterone Constriction of Efferent Arterioles
i. ↓Pc → ↑ Reabsorption
ii. ↓ Renal Blood Flow →
↑ Filtration Fraction → ↑ πc → ↑ Reabsorption
Direct stimulation of Sodium Reabsorption
Stimulation of Na+,K+ ATPase
Stimulation of Na+,H+ Counter-transport
Sodium bicarbonate co transport

14. Effect of Angiotensin-II on Na+ and Water Reabsorption
↑ADH
OVLT→Hypothalamus
Angiotensin-II
↑ thirst
↑ Aldosterone
Constriction of
efferent arterioles
Direct stimulation of
Sodium Reabsorption
↓ Renal Blood Flow
↓Pc
Stimulation of
Na+,K+ ATPase
↑ Filtration Fraction
Stimulation of
Na+,H+
Counter-transport
↑ πc
↑ Reabsorption
↑ Na+ Reabsorption

15. Effect of Angiotensin-II on Na+ and Water Reabsorption
↑ADH
OVLT→Hypothalamus
Angiotensin-II
↑ thirst
↑ Aldosterone
Constriction of
efferent arterioles
Direct stimulation of
Sodium Reabsorption
↓ Renal Blood Flow
↓Pc
Stimulation of
Na+,K+ ATPase
↑ Filtration Fraction
Stimulation of
Na+,H+ Cotransport
↑ πc
↑ Reabsorption
↑ Na+ Reabsorption

16. HORMONES THAT REGULATE ABSORPTION
EFFECTS
Aldosterone
↑ NaCl,H2 O reabsorption, ↑ K+ secretion
Angiotensin -II
↑ NaCl,H2 O reabsorption, ↑H+ secretion
Antidiuretic Hormone
↑H2 O reabsorption
Atrial Natriuretic Peptide
↓ NaCl reabsorption
Parathyroid Hormone
↓ Phosphate Reabsorption ,
↑ Ca++ Reabsorption

17. Anti-diuretic hormone
Site of action
Late distal tubules, collecting tubules, collecting ducts
Binds to specific V2 receptors → movement of an intracellular protein, AQP-2 (Aquaporin-2) to luminal side of cell → molecules of AQP-2 fuse with cell membrane by exocytosis → water channels →↑ water permeability