Potassium Homeostatis Flashcards
What types of injuries result in hyperkalemia?
crush injuries, reperfusion injuries, rhabdomyolysis (death of muscles cells –> release their contents), Tumor lysis syndromes.
What factors upregulate the Na/K ATPase
insulin–> drives pump
cathecolemines (but K+ load does not drive sympathetic nervous system) B2 receptors
Aldosterone
Other factors that impact distribution of K+: plamsa, exercise, cell breakdown, chronic disease
What does insulin do to K+?
increases Na/K ATPase and promotes skeletal and muscle K+ uptake
What effect does pH have on K+
pH down –> K+ up
What effect does increased tonicity have on K+
increases in hydrostatic pressure –> H2O filtration. K+ gets dragged out with water –> increase in intracellular K+. This rise reduces the activity of the Na/K ATPase pump
What happens when you increase sodium absorption in the kidney?
K+ excretion increases
What effect does increased flow rate, caused by say, hyperglycemia have on K+?
K+ never builds up in lumen because you are running water past that channel –> decreased gradient –> K+ exits the cell. K+ ends up in the urine. Serum level indicates hyperkalemia but total body stores are actually insufficient.
Aldosterone effects on K+
increases ENac (Principal cell), increases ROMK in apical membrane (insert vesicles into membrane to form channels), increases Na/K ATPase
RAAS–Ang II
Increase proximal tubule Na+, and distal tubule Na-Cl channel
What triggers BK channel
intracellular potassium levels and flow rates
If RAAS–>aldosterone upregulates sodium resorption, why isn’t their potassium wasting?
Because sodium resporption is upregulated in multiple tubules meaning that there is less sodium than normal once it gets to the ENac channels at the principle cell in the collecting duct. This means that lower than normal amounts of potassium are being excreted.
Which endogenous chemical signal inhibits potassium from crossing the ROMK channel?
Angiotensin II
How will the body compensate if it has high potassium and normal volume?
low angiotension II (remember, it blocks K+ from crossing ROMK channels)
High aldosterone upregulates ROMK. Increases ROMK: ENac ratio
If potassium is high enough, also open BK channels.
In what cell can postassium be resorbed?
Intercalated B
In the ______ cell there K+ is resorbed, what is excreted and where [2]
B intercalated cell; h+ excreted to lumen, HCO3- resorbed into capillary.
