Lecture 6: Calculations and Glucose Flashcards

1
Q

What contributes to final excretion of substances in urine?

A

Degree of reabsorption and secretion of filtered substances

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2
Q

Reabsorption

A

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

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3
Q

Secretion

A

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

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4
Q

If filtered load is greater than excretion rate

A

Net absorption of substance

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5
Q

If filtered load less than excretion rate

A

Net secretion of substance

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6
Q

Reabsorption or secretion rate =

A

Filtered load - excretion rate

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7
Q

Where does glucose reabsorption occur

A

Proximal convoluted tubule

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8
Q

How does glucose get across luminal membrane?

A

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

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9
Q

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

A

GLUT1 or GLUT2

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10
Q

Glucose titration curve shows relationship between?

A

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

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11
Q

As plasma glucose increases

A

Filtered load increases linearly

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12
Q

Why does filtered load increase linearly as plasma glucose increases?

A

It is a freely filtered substance

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13
Q

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

A

< 200 mg/dl

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14
Q

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

A

Above 200 mg/dl

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15
Q

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

A

Above 350 mg/dl

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16
Q

What is Tmax?

A

ALL transporters are saturated, where curve begins to level off

17
Q

Splay

A

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

18
Q

Excretion occurs at what concentrations of glucose

A

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

19
Q

Above 350 mg/dl the excretion curve

A

Increases linearly

20
Q

Glucosuria

A

Excretion/spilling of glucose in urine

21
Q

Why does glucosuria occur in diabetes mellitus?

A

Due to high plasma glucose/hyperglycemia

22
Q

Hyperglycemia

A

High plasma glucose

23
Q

Pregnancy

A

Glucosuria can occur during pregnancy

24
Q

In what glucose transport system can glucosuria occur?

A

Abnormalities/defects in Na+/glucose co-transporter

25
Q

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

A

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

26
Q

Name all conditions that can cause Glucosuria

A

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

27
Q

Fanconi syndrome, disorder in what part of renal tubule?

A

Proximal convoluted tubule

28
Q

Symptoms of Fanconi syndrome

A

Normal glycemia and primary renal glucosuria

29
Q

How is Fanconi syndrome acquired?

A

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

30
Q

How is Fanconi syndrome congenital?

A

Basenji dogs - autosomal recessive trait