Lecture 13 Flashcards
What is tubular reabsorption?
Salt and water go back into peritubular capillaries from the renal tubule
What is tubular secretion?
Unfiltered substances are removed from peritubular capillaries enter renal tubule
What is glomerular filtration?
Filters plasma 20% removed 180 L/day filtrate Plasma membrane = 2.75 L Filtered 65 times/day
What does filtration permit? What does it restrict?
Permits: H2O and small molecules
Restricts: Blood cells and proteins (most!)
What does ultrafiltrate mostly consist of?
Consists of protein free plasma
1% protein filtered (albumin)
What is Dent’s disease?
Patients have mutations in transporter proteins: small molecules weight of protein in urine
How many genes are there in the human genome?
33 000
How many renal genes are there in the human genome?
Several hundred
What kind of animal models are used?
Knockout and transgenic mouse models
What are animal models used for?
Inherited renal disease symptoms
What is included in the Bulk reabsorbing tissue in the Proximal tubule?
70% filtrate 70% H2O and Na ~100% glucose and amino acids 90% HCO3 Lots of energy = lots of mitochondria
What does HCO3 allow?
Control of pH of body fluids
What can be seen in NaPi II knockout mouse?
Struggling to maintain plasma phosphate concentrations ATP levels in body
Phosphates in plasma are important in bone develops as a change
Early abnormal skeletal development
Longitudinal tibial sections show less staining
How many amino acids are there in SGLT 1?
664
How many amino acids are there in SGLT 2?
672
What are SGLT 1 and SGLT 2?
Transmembrane protein: 6 in membrane
Domains span cell membrane, extracellular and intracellular parts of protein
Allow reabsorption of Na and glucose
One protein makes the actual transporter itself
What happens in Familial Renal Glycosuria?
Increased urinary glucose Few gms to more than 100 g/day Normal plasma glucose No general tubule damage 21 mutations in SGLT 2 identified
How is Familial Renal Glycosuria inherited?
Carrier: Heterozygous Autosomal recessive (severe)
Are there any symptoms in Familial Renal Glycosuria carriers?
Technically asymptomatic but may show mild increase in glucose in urine
What protein is involved in bicarbonate reabsorption?
Na-halogen exchanger protein 3
What do Na-halogen exchanger protein 3 do?
Na gradient to take Na in and halogen ions out
Halogen ion is used to reabsorb bicarbonate
Bicarbonate binds to halogen ion to form carbonic acid
Carbonic anhydrase on apical membrane
Aquaporins move water into the cell
Carbonic anhydrase inside the cell dissociates halogen ion and bicarbonate
What do Na cabonate co-transporter protein?
Bicarbonate drives Na out
Reabsorption of bicarbonate into peritubular capillaries and reabsorption of water
What happens when less bicarbonate reabsorption is seen?
Bicarbonate is starting to appear in urine Struggles to maintain plasma bicarbonate Struggles to maintain normal pH Struggles to reabsorb much Na and water Fall in extracellular fluid volume Drop in blood pressure
What happens when systolic blood pressure is hypotensive?
Amount of fluid across proximal tubule reduces because bicarbonate reabsorption decreases
Why does systolic BP become hypotensive?
Inhibition H secretion Inhibition Na and HCO3 transport Fall fluid reabsorption Drop plasma HCO3 pH falls due to HCO3 compensation ECFV falls Therefore BP drops Losing transmembrane protein impacts widely across the body
