K+ and Ca++ regulation Flashcards

1
Q

Two primary functions of K+:

A
  1. cell metabolism

2. ratio of intra/extracellular K+ creates cell resting membrane potential

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2
Q

% of total body K+ stored intracellularly?

A

98%

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3
Q

Total body stores of K+:

A

3,000-4,000 mM

50-55 mM/kg

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4
Q

Two main factors regulating Na-K-ATPase to get K+ back into the cell:

A
  1. insulin

2. catecholamines

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5
Q

Three main ideas with insulin K+ regulation:

A
  1. increases activity of Na-K-ATPase
  2. Promotes skeletal muscle uptake
  3. eating –> inc insulin –> prevents sharp rise in serum K+
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6
Q

How does exercise affect K+ in serum?

A

Muscle cells release K+ –> proportional to degree of exercise

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7
Q

How does serum pH affect K+?

A

H+ uses up bicarb in serum

To balance charge, K+ leaves cell

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8
Q

Acute treatment for acidotic patient with hyperkalemia:

A

Insulin

glucose

Ca++ (to stabilize cardiac myocytes)

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9
Q

% of total body K+ handled by principal cells (late distal tubule and cortical collecting duct):

A

10%

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10
Q

Two principal cell channels facilitating excretion of K+:

A

ROMK

BK

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11
Q

Aldosterone action with respect to K+:

A

Directly stimulated by high K+

Upregulates ROMK

Stimulates Na-K-ATPase

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12
Q

What does Angiotensin II do to ROMK?

A

Inhibits

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13
Q

What can block ROMK to help retain intracellular K+?

A

Mg++

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14
Q

When is BK active?

A

High K+ diet

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15
Q

What is the function of the a-intercalated cell in the distal convoluted tubule/collecting duct?

A

reabsorption of K+

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16
Q

What channels are necessary for K+ reabsorption in the alpha-intercalated cells?

A

K-H-ATPase

H-ATPase

*these two bring K back in from tubule lumen

bicarb also needed to antiport with Cl-

17
Q

PTH generally does what to free calcium?

A

Increase it

18
Q

How does PTH affect kidney role in free Ca?

A
  1. Increases reabsorption?
  2. Increase activation of vit D
  3. Increases PO4 secretion
19
Q

What is active vit D’s role in Ca homeostasis?

A

Increases gut absorption

20
Q

Where is vit D activated?

A

kidney

21
Q

What is PTH regulated by?

A

Ca levels (free)

Increased Ca = decreased PTH

(see page 7 lecture notes)

22
Q

Route of Ca reabsorption in the distal tubule?

A

Transcellularly

23
Q

Pathology that can activate vit D?

A

granulomas

24
Q

What gets released from cortical bone along with calcium by PTH activity?

A

PO4

25
Q

How does free Ca get from inside the cell to the blood?

A

Bound to Calbindin

–> Ca-ATPase