Lecture 18 Renal Regulation of Ion Concentrations Flashcards
what is the normal extracellular concentration of potassium?
140 mEQ/L
a slight increase in extracellular potassium can lead to
cardiac arrest and arrhythmia
an extreme increase in extracellular potassium can lead to
cardiac arrest, fibrillation
kidneys and [extracellular potassium]
kidneys are primary regulator of potassium
they excrete it rapidly and precisely in response to wide variations in intake
overall effect of aldosterone secretion on [potassium]
increase in extracellular [K] stimulates an increase in aldosterone secretion
what part of renal tubules is responsible for K reabsorption?
proximal tubule
ascending limb of henle
what part of renal tubules are responsible for K secretion
late tubule, collecting duct
mechanism of K excretion by principal cells
Na is moved into cell via ENaC pump (from fluid to cell)
K+ is passively secreted from cell to lumen (due to [ ] gradient created by ATPase Na/K+ pump)
what factors stimulate K secretion by principal cells?
[K+] and aldosterone
increase uptake of K cause increase in [K] in plasma
stimulates aldosterone secreiton
relationship between tubular flow rate and potassium secretion
increase in tubular flow increase K+ secretion because it continuously flush K out of fluid (low K in fluid = more secretion)
increase in tubular flow also activates high conductance BK channels that rapidly increase K conductance
why does high sodium intake have little effect on K secretion
high Na+ decreases aldosterone secretion (decreasing K) but also increases tubular flow rate (increasing K) therefore balancing each other out and causing no net change
acidosis
less Ca bound to plasma proteins
pH effect (acidic conditions)
alkalosis
more Ca bound to plasma proteins
pH effect (basic conditions)
effects of PTH
stimulates bone reabsorption
stimulates activation of vitamin D
indirectly increase tubular Ca reabsorption
which factors decrease calcium reabsorption?
increase PTH levels (promotes bone reabsorption by increases [Phosphate]
plasma [phosphate]
metabolic acidosis
what effects does insulin have on extracellular potassium?
stimulates potassium uptake by cells
what effects do catecholamines have on extracellular potassium (beta adrenergic stimulation)
stimulates potassium uptake by cells
what condition is know for an express secretion of aldosterone?
hypokalemia or Conn’s syndrome
what condition is know for deficiency in aldosterone secretion?
hyperkalemia or Addison’s disease
high amounts of potassium in the body due to lack of excretion
effect of metabolic acidosis on extracellular potassium
increases [K]
increases [H] –> decreases Na/K pump activity –> decreases K uptake
effect of metabolic alkalosis on extracellular potassium
decreases extracellular K
what is the effect of cell lysis, strenuous exercise, and increase fluid osmolarity have on extracellular potassium
hyperkalemia (increase [K])
what is the role of intercalated cells in controlling potassium levels?
reabsorb K during depletion
