Lecture 13

Question 1

What is tubular reabsorption?

Answer 1

Salt and water go back into peritubular capillaries from the renal tubule

Question 2

What is tubular secretion?

Answer 2

Unfiltered substances are removed from peritubular capillaries enter renal tubule

Question 3

What is glomerular filtration?

Answer 3

Filters plasma
20% removed
180 L/day filtrate
Plasma membrane = 2.75 L
Filtered 65 times/day

Question 4

What does filtration permit? What does it restrict?

Answer 4

Permits: H2O and small molecules
Restricts: Blood cells and proteins (most!)

Question 5

What does ultrafiltrate mostly consist of?

Answer 5

Consists of protein free plasma

1% protein filtered (albumin)

Question 6

What is Dent’s disease?

Answer 6

Patients have mutations in transporter proteins: small molecules weight of protein in urine

Question 7

How many genes are there in the human genome?

Answer 7

33 000

Question 8

How many renal genes are there in the human genome?

Answer 8

Several hundred

Question 9

What kind of animal models are used?

Answer 9

Knockout and transgenic mouse models

Question 10

What are animal models used for?

Answer 10

Inherited renal disease symptoms

Question 11

What is included in the Bulk reabsorbing tissue in the Proximal tubule?

Answer 11

70% filtrate
70% H2O and Na
~100% glucose and amino acids
90% HCO3
Lots of energy = lots of mitochondria

Question 12

What does HCO3 allow?

Answer 12

Control of pH of body fluids

Question 13

What can be seen in NaPi II knockout mouse?

Answer 13

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

Question 14

How many amino acids are there in SGLT 1?

Answer 14

664

Question 15

How many amino acids are there in SGLT 2?

Answer 15

672

Question 16

What are SGLT 1 and SGLT 2?

Answer 16

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

Question 17

What happens in Familial Renal Glycosuria?

Answer 17

Increased urinary glucose
Few gms to more than 100 g/day
Normal plasma glucose
No general tubule damage
21 mutations in SGLT 2 identified

Question 18

How is Familial Renal Glycosuria inherited?

Answer 18

Carrier: Heterozygous
Autosomal recessive (severe)

Question 19

Are there any symptoms in Familial Renal Glycosuria carriers?

Answer 19

Technically asymptomatic but may show mild increase in glucose in urine

Question 20

What protein is involved in bicarbonate reabsorption?

Answer 20

Na-halogen exchanger protein 3

Question 21

What do Na-halogen exchanger protein 3 do?

Answer 21

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

Question 22

What do Na cabonate co-transporter protein?

Answer 22

Bicarbonate drives Na out

Reabsorption of bicarbonate into peritubular capillaries and reabsorption of water

Question 23

What happens when less bicarbonate reabsorption is seen?

Answer 23

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

Question 24

What happens when systolic blood pressure is hypotensive?

Answer 24

Amount of fluid across proximal tubule reduces because bicarbonate reabsorption decreases

Question 25

Why does systolic BP become hypotensive?

Answer 25

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