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Lecture IV and V: Tubular Transport Mechanisms

Lecture IV and V: Tubular Transport Mechanisms. 25y/o Male With History of Hypertension Family Hx: “Salt-Sensitive” Hypertension PE: BP 170/110 , no JVD, no Edema Fundi: A-V nicking S4 heart sounds, EKG left V-hypertropy Lab: Cushings’s Disease, Pheochromocytoma, Renal

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Lecture IV and V: Tubular Transport Mechanisms

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  1. Lecture IV and V: Tubular Transport Mechanisms

  2. 25y/o Male With History of Hypertension Family Hx: “Salt-Sensitive” Hypertension PE: BP 170/110 , no JVD, no Edema Fundi: A-V nicking S4 heart sounds, EKG left V-hypertropy Lab: Cushings’s Disease, Pheochromocytoma, Renal Artery Stenosis are ruled out PNa - 140 mEq/l, PK 2.5 mEq/l , Low Renin/Aldosterone Post Amiloride, Low Salt Diet 1 month 126/90 3 month 128/85 1 year 120 /88

  3. Early Proximal Tubule, Organic Solute Transport X N a+ Vte = -3 to -6 mV K X K N a

  4. 120 100 80 60 40 20 0 0 20 40 60 80 100 Avid Reabsorption of Organic Solutes in the Proximal tubule [TP]/[P] x 100 Glucose Amino Acids Lactate % Distance Along the Proximal Tubule

  5. Early Proximal Tubule, Bicarbonate Reabsorption N a+ Vte = -3 to -6 mV H+ CO2 + H2O CA K 3HCO3- N a Na K

  6. H2CO3 HCO3-+ CO2 + H2O NaHCO3 CA Early Proximal Tubule, Bicarbonate Reabsorption H+ N a+ Tubular Fluid H+ CO2 + H2O K 3HCO3- N a Na Interstitial Fluid K

  7. 0.9 ( ) ~ 1/3 Kg/day ~ 90% of Filtered Load is Reabsorbed in the Early PT Filtered load = GFR*PHCO3

  8. HA Cl- N a+ Tubular Fluid A- H+ Cl- K+ N a Late Proximal Tubule, Transcellular NaCl Reabsorption

  9. 120 100 80 60 40 20 0 4 0 -4 Solute Concentration Profile in the Proximal tubule Cl- [TF]/[P] x 100 HCO3- Glucose Amino Acids Lactate Vte (mV) 0 20 40 60 80 100 % Distance Along the Proximal Tubule

  10. Late Proximal Tubule, ParacellularNaCl Reabsorption Vte +3 to +6 mV [Cl]TF ~ 140 mEq/l NaCl Tubular Fluid NaCl K N a Interstitial Fluid [Cl]P ~ 105 mEq/l

  11. Isoosmotic Water Reabsorption

  12. 120 100 80 60 40 20 0 4 0 -4 Solute Concentration Profile in the Proximal tubule Cl- Na+, Osmolality [TF]/[P] x 100 HCO3- Glucose Amino Acids Lactate Vte (mV) 0 20 40 60 80 100 % Distance Along the Proximal Tubule

  13. N a+ N a Ascending Thick Limb Transcellular NaCl Reabsorption Na+K+2Cl- Tubular Fluid H+ K+ Cl- K+ HCO3-

  14. Na+K+2Cl- Tubular Fluid N a+ H+ K+ Cl- HCO3- N a Interstitial Fluid Thick Ascending Limb, Lumen Postive Vte Na+,K+,Ca++, Mg++ Vte = +6mV

  15. NaCl H2O Na+K+2Cl- Tubular Fluid N a+ H+ K+ Cl- HCO3- N a Interstitial Fluid The Ascending Limb is Not H20 Permeable

  16. N a Early Distal Tubule NaCl H2O Na+ Cl- Tubular Fluid Cl- Interstitial Fluid

  17. N a Late Distal Tubule & Cortical Collecting Duct Principal Cell H2O Cl- Na+ -ADH Tubular Fluid + ADH K+ K+ Interstitial Fluid

  18. ATP H+ HCO3- N a Late Distal Tubule & Cortical Collecting Duct Na+ Tubular Fluid K+ CO2 + H2O CA K+ Interstitial Fluid

  19. N a Medullary Collecting Duct H2O, Urea Cl- Na+ -ADH Tubular Fluid + ADH K+ Interstitial Fluid

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