04c: K regulation Flashcards
T/F: K is the most abundant cation in body.
True
Most, (X)%, of K is located in which body compartment? At which concentration?
X = 98
ICF;
150 mEq/L
Most K is found in which organ/structure?
Muscle
(X)% of K is in the ECF at (Y) concentration. Plasma K concentration is a (good/poor) indicator of total body K.
X = 2
Y = 3.5-5 mEq/L
Poor
T/F: In response to acute K load, kidney excretion plays key role in maintaining plasma K normal.
False - too slow of a process (hours)
In response to acute K load, (X) process plays key role in preventing life-threatening hyperkalemia. This process is controlled by (Y).
X = uptake of ingested K by cells
Y = hormones
After meal, most of K is taken up into cells via (X) (channel/transporter). List factors that activate (X) and star the most important one.
X = NaK pump
- Rise of plasma K
- Epi
- Insulin*
Subject treated with propranolol (beta adrenergic receptor blocker) will have (reduction/elevation) in plasma K after K load.
Elevation
Why is there a shift of K (into/out of) cells in acidosis?
Out of;
Increased H is buffered within cells, so as it moves in, K moves out
List two mechanisms proposed for loss of K from cells in acidosis.
- Release of protein-bound cellular K
2. Inhibition of NaK pump (due to low pH)
During exercise, there’s increased K movement (into/out of) cells. In which scenario can this be life-threatening?
Out;
Patient on beta-adr. receptor blocker
Increase in osmolality of ECF leads to K movement (into/out of) cells. Why? Give an example.
Out of
(i.e. hyperglycemia);
Cell shrinkage increases intracellular K conc and increases chem gradient for K efflux
To remain in K balance, individual must excrete about (X) K daily in urine. This excretion is regulated by which two factors?
X = 90 mEq
- Plasma K
- Aldosterone
T/F: K is freely filtered at glomerulus.
True
K is filtered at glomerulus at a rate of (X) per day. Most of K is reabsorbed at which tubular locations?
X = 600-900 mEq
PT (80%) and TAL (10%)
At PT, K reabsorption is primarily (passive/active) transport that’s secondary to (X).
Passive diffusion;
X = increased tubular K conc due to water reabsorption
T/F: Transcellular pathway is not involved in K reabsorption.
True
T/F: K reabsorption at PT is downhill.
False - although electrical potential favors K movement into cell, chemical gradient driving K out is much greater
Reabsorption of K at TAL involves mainly (X) transporter/channel at luminal membrane and (Y) transporter/channel at basolateral membrane.
X = NaKCl co-transporter Y = KCl transporter and K channels
T/F: PT, TAL, and distal tubules are capable of either reabsorption or secretion of K.
False - only distal tubules have dual capabilities
Changes in excretion rate of K is handled primarily by (PT/TAL/distal) segments.
Distal
List the cell types that influence K transport in distal nephron. Star the more numerous one, also responsible for (X) ion reabsorption.
X = Na
- Principal* (K secretion)
- Intercalated alpha-type (K reabsorption)
K reabsorption occurs mainly in (cortical/medullary) collecting duct/tubules. And secretion?
Reab: cortical;
Secretion: medullary
List the apical/basolateral transporters and channels involved in K secretion.
NaK pump (basolateral) followed by apical K channels secreting K into tubular lumen
