KIDNEYS BIOCHEMISTRY. Two layers: external – cortex, inner – medulla.
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Transcript of KIDNEYS BIOCHEMISTRY. Two layers: external – cortex, inner – medulla.
KIDNEYS BIOCHEMISTRY
Two layers: external – cortex, inner – medulla.
Functional-structural unit – nephron.
Every kidney – about 1000000 nephrons.
RENAL FUNCTIONS
-Excretion of the end products from the organism (formation of urine)
-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 D3)
-Regulation of blood pressure
-Metabolism of proteins, lipids, carbohydrates, energetic metabolism
Metabolism in kidneys
80 % of water about 10 % of all oxygen 700-900 L of blood/day (25%)carbs – main energetic materialActive:GlycolysisKetolysisTransamination 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: activepassive. 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: activepassive.
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 НСО3
-
- ammonia excretion
MAINTAINING OF ACIDIC-BASE BALANCE BY KIDNEYS
Cells of canaliculusBlood Cavity of canaliculus
Na2HPO4
Na+Na+
HPO42-
Na+
NaH2PO4
Na+
H+ H+
MAINTAINING OF ACIDIC-BASE BALANCE BY KIDNEYS
NaHCO3
Na+
HCO3-
Na+
H2CO3
Na+
H+ H+
H2O CO2
H2O CO2+
H2CO3
HCO3-
BloodCells of
canaliculus Cavity of canaliculus
MAINTAINING OF ACIDIC-BASE BALANCE BY KIDNEYS
NH3+H+
Glutamine
NH4+
NH3
Glutamic acid
MAINTAINING OF ACIDIC-BASE BALANCE BY KIDNEYS
BloodCells of
canaliculus Cavity of canaliculus
HORMONAL ACTIVITY (ERYTHROPOIETIN)
Normal level of oxygen in blood The increased consumption of
oxygen or decreased amount
of erythrocytes
The decrease of oxygen level in blood
Formation of erythropoietin by
kidneys
Erythropoietin stimulation
Bone marrow
Intensified erythropoiesis
Increased number of erythrocytes
The increase of oxygen in blood
Active form of vitamin D -1,25-dihydro-xycholecalci-ferol is formed in kidneys
1,25-dihydroxycholecalciferol
PROPERTIES OF URINE
Amount – 1500-2000 mL/dayPoliuria – diabetes mellitus and insipidusOliguria – heart failure, nephritis, vomiting, feverAnuria – kidney failure, acute intoxication by heavy metals
Color – straw-yellowPale – poliuria (diabetes insipidud)Dark – jaundice, concentrated urineRed – blood availableGreen-blue – decay of proteins in the intestine
Transparency – transparentCloudy – pus or mucin available
Density – 1,003-1,035 g/mLIncreased density – organic or inorganic substances available (diabetes mellitus)Decreased density – diabetes insipidusIsostenuria – continuously low density in oliguria (kidney failure)
pH – 5.5-6.8Acidic – meat food, diabetes mellitus, starvation, feverAlkaline – plant food, cystitis, pyelitis
PATHOLOGICAL COMPONENTS IN URINEHematuria
Macrohematuria
Microhematuria
Causes of hematuria
•Infectious diseases – glomerulonephrotis, pyelonephritis, prostatitis, uretritis, cystitis
•Stones in kidneys and urinary tracts
•Trauma of kidneys and organs of urinary tracts
•Tumors of kidneys and organs of urinary tracts – cancer of kidneys, bladder
PATHOLOGICAL COMPONENTS IN URINEProteinuria
TypePathophysio-logic features
Cause
GlomerularIncreased
glomerular capillary permeability to
protein
Primary or secondary
glomerulopathy
TubularDecreased tubular
reabsorption of proteins in
glomerular filtrate
Tubular or interstitial
disease
Overflow
Increased production of low-molecular-weight
proteins
Monoclonal gammopathy,
leukemia
DehydrationEmotional stress
FeverHeat injury
Inflammatory processIntense activity
Most acute illnessesOrthostatic (postural)
disorder
COMMON CAUSES OF BENIGN PROTEINURIA
Physiological:· Alimentary – (in 30-60 min after carbohydrate food consumption. · Emotional (stress).
Pathological:· Related to hyperglycemia: · Insular – deficit of insulin (diabetes mellitus, pancreatitis). · Extrainsular – disorders of thyroid gland, pituitary functions, liver diseases).· Not related to hyperglycemia – renal glycosuria (normal level of glucose in blood) (renal diabetes).
PATHOLOGICAL COMPONENTS IN URINEGlycosuria
Condition where there is pus or too many white blood cells in the urine
PATHOLOGICAL COMPONENTS IN URINEPyuria
Cloudy urine - pyuria
Causes:
Infectious diseases of kidneys or urinary tract (chlamydia, gonorrhea, viral infections, mycoplasma, fungal infections, tuberculosis), infection of the prostate
Noninfectious causes•treatment with glucocorticoids •mechanical trauma •kidney stones •tumors (benign or malignant)
Brown color of urine- bilirubinuria
Bilirubinuria – appearance of bilirubin in urine
Is the result of direct (conjugated) bilirubin in blood
Causes:•mechanical jaundice•parenchimal jaundice
PATHOLOGICAL COMPONENTS IN URINEBilirubinuria
Causes•overburdening of the liver •excessive RBC breakdown •increased urobilinogen production •a large hematoma •restricted liver function •hepatic infection •poisoning •liver cirrhosis
PATHOLOGICAL COMPONENTS IN URINEUrobilinuria
Urobilinuria – appearance of urobilin in urine
Brown color of urine- urobilinuria
PATHOLOGICAL COMPONENTS IN URINEPhenylketonuria
Appearance of phenylpyruvate in urine
Phenylketonuria - genetically determined disease which is caused by an absence or deficiency of phenylalanine hydroxylase
FeCl3 test