Pi

Question 1

how to calculate filtered load for phosphate

Answer 1

GFR x Plasma concentration x 1

Question 2

how is phosphate reabsorbed in the proximal tubule

Answer 2

80%

• transcellularly
• Na+-Pi transporters

Question 3

what is the role of FGF-23

Answer 3

secreted from the bone in response to PTH, calcitriol, and hyperphosphetemia and inhibits phosphate transporters
–> increases phosphate excretion

Question 4

how does phosphate cross the apical and basolateral membranes

Answer 4

apical: Na+-Pi symporter
basolateral: unkown

Question 5

what enzyme converts calcitriol into its active form

Answer 5

renal 1alpha-hydroxylase

Question 6

what upregulates renal 1alpha-hydroxylase (and thus upregulates calcitriol and calcium and phosphate reabsorption)

Answer 6

low calcium
low phosphate
high PTH

Question 7

what inhibits renal 1alpha-hydroxylase (and thus downregulates calcitriol and calcium and phosphate reabsorption)

Answer 7

high calcium via CaSR

Question 8

effect of PTH on phosphate levels

Answer 8

lowers serum phosphate and increases excretion

Question 9

effect of 1,25(OH)2D3 on phosphate levels

Answer 9

increases serum phosphate by increasing intestinal phosphate absorption

Question 10

effect of insulin on phosphate levels

Answer 10

lowers serum phosphate by increasing uptake of phosphate into cells

Question 11

how does PTH lower serum phosphate levels

Answer 11

inhibits the Na+/Pi transporter and the Na+-H antiporter in the apical membrane of proximal tubule cells

Question 12

how does chronic acidosis affect phosphate levels

Answer 12

increases phosphate excretion

Question 13

how does chronic alkalosis affect phosphate levels

Answer 13

decreases phosphate excretion

Question 14

what can cause phosphaturia

Answer 14

PTH inhibiting the NPT in the proximal tubule

Question 15

what is the route PTH takes from the blood to inhibiting the Na+-Pi transporter

Answer 15

blood –> receptor on basolateral membrane –> activates cAMP –> protein kinase –> phosphorylates the Na+/Pi symporter which inactivates it

Question 16

how much phosphorus of the absorbed amount is secreted into the guy per day

Answer 16

200 mg

Question 17

where is phosphate stored

Answer 17

85% bone
14% cells
1% serum

Question 18

effect of calcitriol on phosphate levels

Answer 18

increases resorption from bone and absorption from intestine

Question 19

how does PTH indirectly increase phosphate reabsorption

Answer 19

indirectly activates intestinal absorption through stimulation of calcitriol production

Question 20

effect of calcitriol on phosphate

Answer 20

increases resorption, reabsorption, and absorption

Question 21

effect of calcitonin on phosphate in the kidneys

Answer 21

promotes phosphate excretion

Question 22

where does PTH decrease reabsorption of phosphate in the nephron

Answer 22

the PCT