Renal Regulation of ECF Potassium Flashcards
What is the formula for potassium balance?
K(bal) = K(in) - K(out)
How much of potassium balance is regulated by the kidneys and by the GI tract?
Renal: 85%
GI: 15%
In response to ß-adrenergic stimulation, what happens to insulin and potassium?
ß-adrenergic stimulation first increases extracellular concentration of potassium and then insulin rises–causing potassium to fall
How are insulin and potassium related?
Inversely–as insulin rises potassium falls, and vice versa
Someone with congenitally low renin (and consequently low aldosterone) would have ________ potassium levels.
high, because aldosterone induces a co-transporter that secretes potassium
What is the most important regulator of extracellular potassium?
insulin
What is the normal serum potassium concentration?
3.5 - 5.0 mM
Although the glomeruli filter only about 30 grams of potassium per day, the kidneys can excrete __________ (because of secretion).
45 grams
How much of the filtered potassium is reabsorbed in the proximal tubule?
80% (through passive diffusion and paracellular movement)
By what process is potassium absorbed in the loop of Henle?
Almost all of the potassium that enters the loop of Henle passes into the cells of the thick ascending loop, but half of that amount seeps back across its electrochemical gradient. Thus, a total of 10% of the original load is absorbed at the TALH.
Which cells in the collecting duct control potassium secretion?
The principal cells
What two proteins are needed to secrete potassium at the level of the collecting duct?
Na/K pumping K into the cells on the basolateral side of the cell, and K channels allowing K to go into the lumen of the collecting duct on the apical side.
High levels of potassium act to increase ________ levels by stimulating the zona glomerulosa of the adrenal gland.
aldosterone
What three things does aldosterone do to principal cells?
Transcribes more Na/K pumps on the basolateral surface
Sends more Na pores to the apical surface (increased reabsorption)
Sends more K channels to the apical surface (which gets excreted in exchange for Na absorption)
Which situation is more likely to lead to hypokalemia, high tubular flow or low tubular flow?
High tubular flow, because the faster flow keeps the potassium gradient steep at the collecting duct, thus ensuring more flow of potassium.
