Term
| What is the normal range of plasma K+? |
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Definition
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Term
| What percentage of filtered K+ is normally reabsorbed? |
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Definition
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Term
| What are the primary sites for K+ reabsorption? |
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Definition
| Proximal tubule, thick ascending limb of Henle’s loop, and medullary collecting duct |
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Term
| What are the primary sites for K+ secretion? |
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Definition
| Late distal tubule and cortical collecting duct |
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Term
| What protein transporter does Lasix/Furosemide affect? |
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Definition
| It inhibits the NKCC transporter in the thick ascending loop of Henle |
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Term
| Where is most of the potassium secreted in a high potassium diet? |
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Definition
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Term
| What are the two types of collecting duct cells? And which secretes and which reabsorbs potassium? |
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Definition
Principal cells – secrete K+
Intercalated cells – reabsorb K+ |
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Term
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Definition
| Renal outer medullary potassium channels. They secrete potassium in normal diets. |
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Term
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Definition
| Big potassium channels. They are like a safety gauge – they are normally closed but they open during hyperkalemia and secrete potassium. |
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Term
| What happens to BK and ROMK channels during hypokalemia? |
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Definition
| BK channels close and ROMK channels are sequestered intracellularly |
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Term
| What is the luminal potential as referenced to the blood? |
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Definition
-40 mV
*when potassium channels are open, K+ will leak into the urine because it is attracted to the negative charge |
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Term
| How do arterial concentrations of K+ affect aldosterone release? |
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Definition
| Hyperkalemia stimulates aldosterone release from adrenal cortex |
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Term
| What protein channels does Amiloride affect? |
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Definition
| It inhibits ENaC (epithelial sodium channels) which inhibits Na reabsorption in the late distal convoluted tubules and collecting ducts. This promotes loss of Na and water from the body |
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Term
| Is Amiloride K+ wasting or K+ sparing? |
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Definition
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Term
| How does Spironolactone/Aldactone work? |
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Definition
| It is a competitive antagonist of the aldosterone receptor |
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Term
| Is Spironolactone K+ wasting or K+ sparing? |
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Definition
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Term
| What are the 6 factors that increase K+ secretion in the distal nephron? |
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Definition
1. high plasma potassium
2. aldosterone
3. high Na+ delivery to distal nephron
4. high flow rate in distal nephron
5. high potassium diet
6. nonchloride anions in distal nephron |
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Term
| What is the mechanism of K+ wasting diuretics? |
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Definition
Block Na+ reabsorption
Increased Na+ in tubules stimulates Na/K ATPase downstream which increases Na+ reabsorption and K+ secretion |
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Term
| How do K+ sparing diuretics work? |
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Definition
| By inhibiting the Na/K ATPase pump or by decreasing the apical membrane permeability to Na+ inward diffusion |
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Term
| What does enhanced secretion of K+ cause? |
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Definition
| Hypokalemic metabolic alkalosis = an increase in H+ secretion which depletes the blood of protons |
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Term
| Why is it counterintuitive to diagnose hypokalemic metabolic alkalosis from a urine sample? |
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Definition
| The urine sample is acidic due to high content of protons |
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