Lecture 6: Calculations and Glucose

Question 1

What contributes to final excretion of substances in urine?

Answer 1

Degree of reabsorption and secretion of filtered substances

Question 2

Reabsorption

Answer 2

Water and solutes such as Na, Cl, HCO3, glucose, AA, urea, Ca, Mg, phosphate, lactate, citrate are all reabsorbed

Question 3

Secretion

Answer 3

Organic acids and bases, K, some urea, typically secreted into tubular fluid from peritubular capillaries

Question 4

If filtered load is greater than excretion rate

Answer 4

Net absorption of substance

Question 5

If filtered load less than excretion rate

Answer 5

Net secretion of substance

Question 6

Reabsorption or secretion rate =

Answer 6

Filtered load - excretion rate

Question 7

Where does glucose reabsorption occur

Answer 7

Proximal convoluted tubule

Question 8

How does glucose get across luminal membrane?

Answer 8

Na+/glucose co-transporter (aka SGLT 1)

Question 9

How does glucose get reabsorbed from proximal tubule cell into blood?

Answer 9

GLUT1 or GLUT2

Question 10

Glucose titration curve shows relationship between?

Answer 10

Plasma glucose concentration (x axis) and reabsorption (y axis)

Question 11

As plasma glucose increases

Answer 11

Filtered load increases linearly

Question 12

Why does filtered load increase linearly as plasma glucose increases?

Answer 12

It is a freely filtered substance

Question 13

At what plasma glucose concentration is all filtered glucose reabsorbed up to? (So less than this concentration)

Answer 13

< 200 mg/dl

Question 14

Above what value of glucose concentration are transporters limiting and the glucose curve starts to bend?

Answer 14

Above 200 mg/dl

Question 15

At what glucose concentration are all transporters saturated and curve levels off?

Answer 15

Above 350 mg/dl

Question 16

What is Tmax?

Answer 16

ALL transporters are saturated, where curve begins to level off

Question 17

Splay

Answer 17

Reabsorption approaching saturation glucose level to show up in urine before Tmax reached

Question 18

Excretion occurs at what concentrations of glucose

Answer 18

Above 200 mg/dl, not all carriers saturated but some excretion due to a lot of them being sautrated

Question 19

Above 350 mg/dl the excretion curve

Answer 19

Increases linearly

Question 20

Glucosuria

Answer 20

Excretion/spilling of glucose in urine

Question 21

Why does glucosuria occur in diabetes mellitus?

Answer 21

Due to high plasma glucose/hyperglycemia

Question 22

Hyperglycemia

Answer 22

High plasma glucose

Question 23

Pregnancy

Answer 23

Glucosuria can occur during pregnancy

Question 24

In what glucose transport system can glucosuria occur?

Answer 24

Abnormalities/defects in Na+/glucose co-transporter

Question 25

Abnormalities/defects in Na+/glucose co-transporter cause what?

Answer 25

Tmax decreases, so takes less saturation of glucose to cause all carriers to be booked

Question 26

Name all conditions that can cause Glucosuria

Answer 26

Diabetes mellitus Pregnancy Defects in Na+/glucose co-transporter High stress Fanconi syndrome

Question 27

Fanconi syndrome, disorder in what part of renal tubule?

Answer 27

Proximal convoluted tubule

Question 28

Symptoms of Fanconi syndrome

Answer 28

Normal glycemia and primary renal glucosuria

Question 29

How is Fanconi syndrome acquired?

Answer 29

Certain drugs, exposure to heavy metals, Vitamin D deficient, Kidney transplant

Question 30

How is Fanconi syndrome congenital?

Answer 30

Basenji dogs - autosomal recessive trait