Lecture 18 - Renal Regulation Of [ion] Flashcards
The normal [K]ecf is _______.
A. 142 mEq/L ( 0.3mEq/L)
B. 4.2 mEq/L ( 0.3mEq/L)
C. 150 mEq/L
D. 5 mEq/L
B. 4.2 mEq/L ( 0.3mEq/L)
ECF contains approximately what % of body K?
A. 1%
B. 5%
C. 25%
D. 79%
A. 1%
An increase in ECF [K] of _____ may lead to the development of cardiac arrhythmia.
3-4 mEq/L
Normal ICF [K] is _______.
A. 140 mEq/L ( 0.3mEq/L)
B. 4.2 mEq/L ( 0.3mEq/L)
C. 150 mEq/L
D. 5 mEq/L
A. 140 mEq/L ( 0.3mEq/L)
ECF potassium is directly controlled in what two portions of the nephron?
DCT and collecting ducts
Aldosterone is a stimulator/inhibitor of potassium secretion
stimulator (increased aldosterone increases potassium loss)
Potassium reabsorption occurs in the:
A. PCT and late DCT
B. Ascending limb of LoH
C. Collecting duct and PCT
D. PCT and ascending LOH
D. PCT and ascending LoH
Potassium secretion/sodium reabsorption occurs via the ____ in principal cells.
Na/K ATPase
Na+ is reabsorbed; K+ is secreted
K+ flow through ____ on the apical membrane
K+ channel
High K+ plasma produces an ____ in aldosterone, as well as direct K+ secretion in the ______.
Increase
cortical collecting tubules
Approximately 50% of Ca2+ is found ______ proteins.
bound to transport
Changes to ___ will affect the binding of Ca2+ to transport proteins
A. Cell size
B. Blood volume
C. Body temp
D. pH
D. pH (changing pH will change proteins)
Acidosis results in a ____ of protein bound Ca2+.
A. Decrease
B. Increase
C. No change
A. decrease
Release of _____ causes an increase in blood calcium levels.
PTH
PTH works to raise blood [Ca2+] by _____.
increasing bone breakdown; increasing Ca2+ absorption in the GI tract; increased Vit. D3 activation; increased tubular reabsorption (indirectly)
What % of Ca2+ is reabsorbed by the PCT?
A. 99%
B. 65%
C. 50%
D. 22%
B. 65%
20% of calcium is absorbed in the PCT by what routes?
Transcellular
- Electrochemical gradient “pushes” Ca2+ out of the lumen
- Basolateral Ca2+ ATPase
- Basolateral Na+/Ca2+ exchanger
Calcium resorption in the loop of Henle is in the _______.
A. Thick descending
B. Thick ascending
C. Thin descending
D. Thin ascending
B. Thick ascending
50% of calcium absorption in the thick ascending loop of Henle occurs by paracellular routes. The remaining 50% occurs through the transcellular route and is stimulated by ______.
A. Calcitonin
B. PTH
C. Aldosterone
B. PTH
T/F: Ca2+ reabsorption occurs in all portions of the nephron.
False; Ca2+ reabsorption is relegated to the PCT, DCT, and thick ascending Loop of Henle
Ca2+ reabsorption of calcium is accomplished by ____ stimulated by PTH.
A. Sodium/Calcium exchanger on the basolateral side
B. Sodium/Calcium exchanger on the apical side
C. Calcium ATPase on the basolateral side
D. Calcium ATPase on the apical side
C. Calcium ATPase on the basolateral side
Phosphate excretion occurs via what mechanism?
overflow (Tmax=0.1mM/min)
Resorption of phosphate occurs via a ____cellular route.
A. paracellular
B. trans
B. trans
____ assists in both resorption of Ca2+ and PO4
PTH
PTH causes phosphate to exceed its transport maximum; this results in _____.
phosphate excretion
Of insulin, chatecholamines, and aldosterone, which produce potassium uptake?
all three
Describe the mechanism of action of aldosterone in regard to potassium reabsorption
1) Aldosterone stimulates Na/ATPase pumps in principal cells
2) Luminal membrane permeability for K+ increases
3) Extracellular [K+] increases
Describe the effect of metabolic acidosis on ECF [K+]
Acidosis (decreased pH= increased [H+]) produces changes to the proteins comprising the Na/KATPase pumps. This produces decreased re-uptake of K+ into the cells.
Describe the effect of cell lysis on ECF [K+]
Increased, as lysis of cells releases large amounts of the ICF K+
Describe the effect of metabolic alkalosis on ECF [K+]
Decreases extracellular K+
Principle cells are responsible for (secretion/absorption) of K+.
Secretion
Principal cells are located in what portion of the nephron?
A. DCT
B. Cortical collecting tubule
C. Medullary collecting tubule
D. DCT & Cortical collecting tubule
D. DCT and cortical CT
Principle cells secrete K+ what what mechanism?
Na/K ATPase on the basolateral membrane
passive diffusion of K+ into tubular lumen
Intercalated cells resorb K+ during what situation?
A. Increased ECF K+
B. Decreased ECF K+
C. Decreased tubular K+
B. Decreased ECF K+ (K+ depletion)
Intercalated cells move K+ and what other ion during K+ depletion? Is this sym- or anti-port?
H+; anti-port (H+ is secreted)
_____ intercalated cells secrete K+
Type B
______ of the late distal and collecting tubules reabsorb K+
Type A intercalated cells
By what mechanisms are internal [K] regulated?
Decreased ECF [K]
1) insulin - increases cellular K uptake
2) aldosterone - stimulates cellular K uptake
3) beta-adrenergic stimulation - increases cellular K uptake
Increased ECF [K]
4) acid/base disturbances - decreased pH can increase [K]ecf. The mechanism is unclear, but it’s believed to arise from decreased Na/KATPase function 2/2 acidosis*
5) cell lysis - spills out ICF potassium
6) exercise - myocytes release K with strenuous exercise
7) increased ECF Osmolarity - Complicated! Increased ECF Osmolarity promotes diffusion of water out of cells. This, in turn, raises ICF [K]. When this increase in ICF [K] occurs, K flows down its gradient into the ECF fluid.
*Remember that pumps are proteins. A change in pH affects the structure of the protein.
Potassium excretion is primarily controlled by the _____ of the late distal and cortical collecting tubules.
Prinicpal (Think “Principal Potassium”)
Outline the process of potassium excretion by the kidneys.
1) Increased blood [K] occurs
2) K is absorbed into renal tubule cells by basolateral Na/KATPase
3) ICF [K] is raised
4) K flows down its gradient into the tubular lumen
- occurs in prinicpal cells
- “ROMK”-renal outer medullary potassium channels
- “BK”- “Big Potassium” channels
In severe K depletion, the ____cells act to resorb K.
A. Principle cells
B. Type A Intercalated cells
C. Type B Intercalated cells
B. Type A Intercalated cells
In cases of excess potassium, the _____ act in concert with principal cells to secrete potassium.
A. Principle cells
B. Type A Intercalated cells
C. Type B Intercalated cells
C. Type B Intercalated cells
These are under control of aldosterone
This hormone sees its secretion increased when ECF [K] begin to rise.
A. ADH
B. Epinephrine
C. Aldosterone
D. Erythropoietin
C. Aldosterone
