Presentation on theme: "Biochemistry of kidney and urine. Two layers: external – cortex, inner – medulla."— Presentation transcript:
Biochemistry of kidney and urine
Two layers: external – cortex, inner – medulla.
Functional- structural unit – nephron. Every kidney – about nephrons.
RENAL FUNCTIONS -Excretion of the end products from the organism (formation of urea) -Maintenance of acidic-base balance -Maintenance of water-salt balance -Maintenance of osmotic pressure -Hormonal activity rennin synthesis (blood pressure regulation) erythropoietin (erythrocytes formation), 1,25-dihydroxycholecalcipherol (vitamin D 3 ) -Regulation of blood pressure -Metabolism of proteins, lipids, carbohydrates, energetic metabolism
Metabolism in kidneys 80 % of water about 10 % of all oxygen L of blood/day (25 %) carbs – main energetic material Active: Glycolysis Ketolysis Transamination and deamination
Urine formation Structures responsible for the urine formation: glomeruli, proximal canaliculi, distal canaliculi. Mechanism of urine formation: filtration reabsorption secretion
Mechanisms of elimination: filtration reabsorption excretion
About 120 mL/min or 180 L/day of blood is filtrated. Filtration – passive process. After filtration – primary urine (180 L/day) Filtration Takes place in glomeruli. Substances with molecular mass below 40,000 Da pass through the membrane of glomerulus into capsula.
Filtration is caused by: -hydrostatic pressure of blood in capillaries of glomeruli (70 mm Hg) -oncotic pressure of blood plasma proteins (30 mm Hg) -hydrostatic pressure of ultrafiltrate in capsule (20 mm Hg) 70 mm Hg-(30 mm Hg+20 mm Hg)=20 mm Hg Hydrostatic pressure in glomeruli is determined by the ratio between diameter of ascendant and descendant arteriole
Reabsorption: active passive. Lipophilic substances - passive. Na/K АТP-аse is very active Reabsorption Takes place in proximal and distal canaliculi. What is reabsorbed? Glucose (100%), amino acids (93%), water (98%), NaCl (70%) etc. The urine is concentrated (toxins damages the proximal canaliculi)
Takes place in proximal and distal canaliculi. Secretion: active passive. Passive secretion depends on the pH. What is secreted? Ions of K, аmmonia, H + drugs xenobiotics Secretion Transport of substances from blood into filtrate.
CLEARANCE Clearance of any substance is expressed in ml of blood plasma that is purified from this substance for 1 min while passing through the kidneys. About 180 L of primary urine is formed for 1 day, about 125 mL of primary urine for 1 min. Glucose is reabsorbed completely; clearance = 0 Inulin is not reabsorbed absolutely; clearance = 125 mL/min If clearance is more than 125 mL/min the substance is secreted actively. Clearance = (C urine/C plasma) * V
REGULATION OF BLOOD PRESUURE BY KIDNEYS
REGULATION OF BLOOD PRESSURE BY KIDNEYS Inadequate supply of blood to kidneys (decrease of blood pressure, hypovolemia) Constriction of arterioles Irritation of juxtaglomerular cells Rhenin Angitensinogen Angiotensin І Angiotensin ІІ Angiotensin-converting enzyme Vasocostriction The increase of blood pressure Secretion of aldosteron Reabsorption of Na and water The increase of blood volume
REGULATION OF BLOOD PRESSURE BY KIDNEYS The decrease of blood pressure, hypovolemia The decrease of blood volume in atriums and carotid sinuses Reaction of volume-receptors Stimulation of vasopressine formation Impulses to hypothalamus Activation of hyaluronidase in kidneys canaliculi Depolimeralisation of hyaluronic acid The increase of water reabsorption The increase of blood volume The increase of blood pressure
Three mechanisms: -Conversion of two substituted phosphates into one substituted in the cavity of canaliculi - Formation of carbonic acid in the cells with the following dissociation to Н + and НСО ammonia excretion MAINTAINING OF ACIDIC-BASE BALANCE BY KIDNEYS
Cells of canaliculus BloodCavity of canaliculus Na 2 HPO 4 Na + HPO 4 2- Na + NaH 2 PO 4 Na + H+H+ H+H+ MAINTAINING OF ACIDIC-BASE BALANCE BY KIDNEYS
NaHCO 3 Na + HCO 3 - Na + H 2 CO 3 Na + H+H+ H+H+ H2OH2OCO 2 H2OH2O + H 2 CO 3 HCO 3 - Blood Cells of canaliculus Cavity of canaliculus MAINTAINING OF ACIDIC-BASE BALANCE BY KIDNEYS
NH 3 +H + Glutamine NH 4 + NH 3 Glutamic acid MAINTAINING OF ACIDIC-BASE BALANCE BY KIDNEYS Blood Cells of canaliculus Cavity of canaliculus