Gene models & nephron function Flashcards
What % of plasma is filtered into Bowman’s capsule?
20%
What is tubular secretion?
movement from peritubular capillary
What is the diameter of the glomerulus?
20um
How much plasma is filtered per day?
180 litres/day filtrate
Describe the level of energy needed for glomerular filtration to take place
High levels of energy
What arteriole carries blood into the glomerular capillaries?
afferent arteriole
What arteriole carries blood out of the glomerular capillaries?
efferent arteriole
What does the glomerulus permit across its membrane?
H20 & small molecules
What does the glomerulus restricts across its membrane?
blood cells & proteins
What is ultra-filtrate composed of?
- consists of protein free plasma
- 1% protein filtered (albumin) - usually reabsorbed by the proximal tubule
What can proteins in urine be a sign of?
UTI
What is movement from the lumen of the nephron into peritubular called?
transcellular reabsorption
What is movement from the peritubular capillary into the lumen of tubule called?
transcellular secretion
What is movement in both directions between the lumen of tubule & peritubular capillary called?
Paracellular secretion or reabsorption
What is transcellular reabsorption called?
transport using transport proteins, transpiring ion solutes + water into cell across membrane
What does paracellular movement move?
Between cell
How many genes does the human genome have?
33,000 genes
How many renal genes does a human have?
Several hundred
How much reabsorption takes place in the proximal tubule?
- 70% (H2O & Na+)
- approx 100% glucose & amino acids
- 90% HCO3 (bicarbonate)
- high levels of mitochondria to allow energy-requiring processes to occur
What ATPase is found on the proximal tubule basolateral membrane?
sodium-potassium ATPase
What membrane are potassium channels found on in the basolateral membrane?
basolateral
Describe the intracellular sodium concentration in the proximal tubule
low
What cotransporters are involved on the apical surface of the proximal tubule involved in the movement pf sodium & glucose into the cell?
SGL T1 & SGL T2
What is the sodium phosphate cotransporter (NaPiII) involved in?
The movement of phosphate into cell
What are the results of NaPiII knockout mouse phenotype?
- Less Pi reabsorption
- More lost in urine
- Issues renal mineralisation
(renal mineralisation - renal stone/crystal formation)
What is the importance of phosphate?
- bone formation
- used for ATP
What staining is used to see the NaPiIIa knockout in a mouse?
Von Kossa staining - lots of dark-stained sports indication of mineralisation
What occurs as a result of low intracellular sodium concentration?
creates an electrochemical gradient for cotransporter to move sodium into the cell & hydrogen out of the cell
What happens to the hydrogen once it has left the cell?
it binds to HCO3 (bicarbonate), forming H2CO3 (carbonic acid). Carbon anhydrase then moves CO2 & H20 into the cell. Intracellular anhydrase then moves bicarbonate out of the cell via the basolateral exit
Why is reabsorption of bicarbonate important?
regulates the pH of the body
What is the effect of knocking out the NHE3 gene?
struggle to reabsorb plasma bicarbonate (HCO3), and a lower pH due to lack of pH regulation
What is the relationship between plasma glucose concentration & plasma glucose reabsorption?
linear relationship
When does plasma glucose concentration not have a linear relationship with plasma glucose reabsorption?
when there is no more free carriers for reabsorption
What is the renal threshold?
concentration of a substance dissolved in the blood above which the kidneys begin to remove it into the urine
What is the inherited disease given to those whose sodium-glucose carriers don’t work?
diabetes
What 2 systems are used to remove substances from the proximal tubule?
organic cations & organic anions
What is the function of the Loop of Henle?
- concentration of the urine
- reabsorption of Na+, Cl-, H2O
- reabsorption of Ca2+ & Mg2+
- site of action of loop diuretics
What are the 3 parts of the loop of Henle?
- descending limb
- thin ascending limb
- thick ascending limb
What size diameter is the descending limb?
thin
What leaves in the thin descending limb?
water
what leaves in the ascending limb?
sodium & chloride
What is the purpose for water leaving in the descending limb & sodium & chloride leaving in the thin ascending limb?
creates osmotic gradient which allows for water reabsorption
What leaves the thick ascending limb?
1 sodium, 1 potassium, 2 chloride ions released into the intracellular compartment
How does sodium leave the body?
via a sodium ATPase
What is needed for the CLCK channel to reabsorb chloride?
Barttin (beta subunit)
What does ROMK allow?
potassium reabsorption
What does Bartter’s syndrome lead to?
problem with sodium & chloride reabsorption
- hypotension (due to reduced ECF)
- kypokalaemia
- metabolic alkalosis
- hypercalciuria (calcium in urine)
- nephrocalcinosis - kidney stones
What is the biological effect of inability to produce barttin?
faulty CLCK
What do diuretics do?
increase urine, therefore reducing high blood pressure
What are people with Barter’s syndrome unlikely to experience?
hypertension
What occurs in the early distal tubule?
- reabsorption of Na + Cl
- reabsorption of Mg2+
- sensitive to thiazine diuretics