Renal Tubular Reabsorption and Secretion PDF

12/20/24 Renal tubular Reabsorption and 1 Secretion Derek Owens DrAP, CRNA 1 2 Module 3 ´ Guyton 26, 27, 28, 29, 30 ´ Learning Objectives 1. Describe the structure and function of the renal and urologic systems. 2...

12/20/24 Renal tubular Reabsorption and 1 Secretion Derek Owens DrAP, CRNA 1 2 Module 3 ´ Guyton 26, 27, 28, 29, 30 ´ Learning Objectives 1. Describe the structure and function of the renal and urologic systems. 2. Differentiate the various functions of the kidney and how it maintains optimal cell and tissue metabolism. ´ Guyton chapter 28 2 3 Reabsorption and secretion ´ Urinary excretion = glomerular filtration - tubular absorption + tubular secretion 3 1  12/20/24 4 Active reabsorption of proteins ´ Pinocytosis 4 Tubular reabsorption 1. Large amount of glomerular filtration 2. Tubular reabsorption is highly selective 5 5 Tubular reabsorption mechanisms 1. Across tubular epithelial membranes 2. Through the peritubular capillary membrane 6 6 2  12/20/24 7 Active transport 1. Primary active transport 2. Secondary active transport 7 8 Transported through or between epithelial cells ´ Paracellular path ´ Transcellular path 8 Primary active transport ´ Concentration gradient ´ Electrochemical gradient 9 9 3  12/20/24 Summary of sodium reabsorption 1. Down an electrochemical gradient 2. ATPase pump 3. Peritubular capillary reabsorption 10 10 Secondary active reabsorption ´ Two or more substances ´ One down its electrochemical gradient ´ Does not require energy from ATPase 11 11 12 Secondary active secretion ´ Counter transport 12 4  12/20/24 13 Transport Maximum ´ Limit of active reabsorption mechanisms 13 No transport Maximum ´ The electrochemical gradient ´ Membrane permeability ´ Time of fluid within the tubule 14 14 Passive water reabsorption ´ Proximal tubule ´ Loop of Henle ´ Collecting tubule 15 15 5  12/20/24 16 Chloride reabsorption ´ Passive ´ Secondary active transport 16 17 Waste reabsorption ´ Urea ´ Creatinine 17 Proximal tubular reabsorption 1. Large numbers of mitochondria 2. Large brush border 3. Extensive intracellular and basal channels 18 18 6  12/20/24 19 Proximal tubule solute concentration changes ´ Sodium ´ Glucose ´ Amino acids ´ Bicarbonate 19 20 Loop of Henley ´ Thin descending segment ´ Thin ascending segment ´ Thick ascending segment 20 Thick ascending limb Na/K pump 21 21 7  12/20/24 22 Distal tubules Diluting segment 22 Late distal tubule and cortical collecting tubules ´ Principal cells ´ Intercalated cells 23 23 Principal cells of the late distal tubules and cortical collecting tubules ´ Sodium reabsorption ´ Potassium secretion 24 24 8  12/20/24 Intercalated cells of the late distal tubules and cortical collecting tubules ´ Type A ´ Type B 25 25 26 Summary of the late distal tubule and cortical collecting tubule 1. Impermeable to urea 2. Aldosterone controlled sodium reabsorption 3. Potassium secretion 4. Type A intercalated cells secrete hydrogen 5. Type B intercalated cells secrete bicarbonate 6. Water from ability is controlled by vasopressin 26 27 Medullary collecting ducts 1. ADH controlled water permeability 2. Permeable to urea 3. Secrete hydrogen 27 9  12/20/24 Concentration of solutes in different tubular segments 28 28 29 Regulation of tubular reabsorption 1. Glomerulotubular balance 2. Peritubular capillary and renal interstitial fluid physical forces 3. Arterial pressure 4. Hormonal control 29 30 Glomerulotubular Balance ´ Increased tubular load.65 x 125 = 81.25.65 x 150 = 97.5 30 10  12/20/24 Peritubular capillary and renal interstitial fluid physical forces ´ Hydrostatic pressure ´ Colloid osmotic forces ´ Large filtration coefficient NFP= (Pc - Pif)-(Ωp - Ωif) Reabsorption = K f x Net forces NFP = (13 – 6) – (32 – 15) NFP = (7) – (17) 31 NFP = -10 31 32 Peritubular capillary physical forces ´ Hydrostatic 1. Arterial pressure 2. Renal arteriole resistance ´ Osmotic 1. Systemic osmotic pressure 2. The filtration fraction Reabsorption = K f x Net forces 32 Renal interstitial pressures Peritubular capillary reabsorption 33 33 11  12/20/24 34 Pressure natriuresis and diuresis ´ GFR autoregulation ´ Decreased reabsorption ´ Decreased Angiotensin II ´ Internalization of sodium transporter proteins 34 35 Hormones that control tubular reabsorption ´ Aldosterone ´ Angiotensin II ´ Anti-diuretic hormone ´ Atrial natriuretic peptide ´ Parathyroid hormone ´ Sympathetic stimulation 35 36 Aldosterone ´ Principal cells of the cortical collecting tubule ´ Increased extra cellular potassium concentration ´ Increased angiotensin II levels 36 12  12/20/24 37 Angiotensin II 1. Stimulates aldosterone secretion 2. Constricts the efferent arterioles 3. Directly stimulates sodium reabsorption 37 Anti-diuretic hormone (ADH) ´ Distal tubule ´ Collecting tubule ´ Collecting duct epithelia 38 38 39 Atrial natiuretic peptide ´ Inhibits sodium and water reabsorption ´ Inhibits renin secretion 39 13  12/20/24 40 Parathyroid hormone ´ Calcium reabsorption ´ Phosphate secretion ´ Magnesium reabsorption 40 41 Sympathetic nervous system ´ Alpha adrenergic receptors 41 42 Renal clearance ´ Renal blood flow ´ GFR US x V CS = ´ Tubular reabsorption Ps ´ Tubular secretion 42 14  12/20/24 43 Inulin clearance ´ Not reabsorbed or secreted US x V GFR = Ps 43 44 Creatinine clearance ´ Cleared by glomerular filtration ´ Slightly secreted U Cr ! # GFR = C cr = P Cr 44 45 Renal plasma flow ´ Filtration fraction ´ Tubular reabsorption and secretion 45 15