Renal Regulation of Electrolytes Flashcards
What 2 mechanisms are in charge of K+ homeostasis?
- K+ regulation mechanisms in the ECF
- Mechanisms adjusting renal K+ excretion to match dietary K+ intake
Where is most of the K+ in the body found?
In the ICF
How is the rapid rise in K+ in the ECF prevented after a meal?
This rise in plasma [K+] is prevented by the rapid (minutes) uptake of K+ into cells.
What is the effect of aldosterone, insulin and epinephrine on plasma [K+]?
It results in movement of K+ into the cells and decreases the plasma [K+]
What does epinephrine on alpha receptors stimulate?
K+ release from cells
What does cell lysis stimulate?
K+ release from cells
What does hyperosmolarity stimulate?
K+ release from cells due to cells shrinking and increasing the driving force on K+
What does epinephrine on beta-2 receptors stimulate?
K+ uptake into cells
What does aldosterone stimulate?
Stimulates the Na/K pump which increases the K+ excretion
What does hyposmolarity stimulate?
K+ uptake into cells as they swell and dilute the K+ inside the cell the driving force no the K+ going into the cell is increased.
What is the normal reabsorption of K+ in the kidneys?
85%
What are the 3 factors that regulate the rate of K+secretion by the DT and CD?
- Na/K ATPase Pump Actvity
- Tubular Cell to Tubular Lumen Gradient
- K+ Permeability of Apical Membrane
What is the effect of increased extracellular K+?
It stimulates the Na/K ATPase which leads to increased [K+] within the cell and this leads to increased K+ permeability of the apical membrane and results in increased K+ secretion.
Increased ECF [K+] will also increase aldosterone which will increase the K+ secretion via stimulation of Na/K ATPase pump
What is the effect of glucocorticoids on K+ secretion?
It will increase it indirectly by increasing the GFR
What is the effect of ADH on K+ secretion?
It has no net effect on the K+ secretion
Why does ADH have no net effect on K+ secretion?
This is due to the secretion of ADH occurring during antidiuresis which means the effect of ADH in increasing the K+ secretion would be opposed by the effect of the decreased urinary flow rate decreasing the K+ secretion.
These two effects cancel out and so the ADH had no effect on the K+ secretion.
What is the effect of increased DT flow rate on K+?
It will lead to increased K+ secretion but also decreased ADH. Decreased ADH will result in less active Na/K ATPase which will lead to decreased K+ secretion. These opposing effects will decrease or maintain the K+ balance.
What is the effect of decreased DT flow rate on K+?
It will lead to decreased K+ secretion but also increased ADH. Increased ADH will result in more active Na/K ATPase which will lead to increased K+ secretion. These opposing effects will increase or maintain the K+ balance.
What is the effect of acute metabolic acidosis on K+ secretion?
It will decreased the K+ permeability of the apical membrane in the DT and CD and this will lead to decreased K+ secretion and excretion.
What is the effect chronic metabolic acidosis on K+ secretion?
It will lead to increased K+ out exchange for H+ in exchange which will lead to increased plasma [K+]. This increase will activate the aldosterone system and increased the permeability of the apical membrane in the DT and CD and lead to increased K+ secretion and excretion.
What is the effect of furosemide, acetazolamide and mannitol on K+?
K+ wasting
What is the effect of spironolactone and amiloride on K+?
K+ sparing
Where is most of the Ca2+ in the body stored?
99% of the Ca in the body is stored in the bone
What is the general form that Ca is found as in the body?
Half of the Ca is found in the ionized form and half is found bound to protein
What happens to Ca in the case of acidosis?
Increases the ionized Ca -> hypercalcemia
What happens to Ca in the case of alkalosis?
Decreased the ionized Ca -> hypocalcemia
What is the effect of increased calcitriol on Ca?
It will increase the renal absorption of Ca2+
What is the function of parathyroid hormone?
It protects against low [Ca2+]
What is the function of calcitriol?
It protects against low [Ca2+]
What is the function of calcitonin?
It protects against high [Ca2+]
What is the effect of PTH as Ca decreases?
It will lead to increased reabsorption of Ca by the kidneys and increase bone resorption as well as increased levels of calcitriol.
All of this will lead to increased [Ca2+]
What is the effect of calcitriol on decreased Ca levels?
The parathyroid will increase calcitriol production with decreased [Ca2+]. Calcitriol increases the Ca2+ resorption from bone and decreases Ca2+ excretion in the kidneys.
What is the effect of calcitonin on high levels of [Ca2+]?
Increases in Ca will increase the levels of calcitonin. It will lead to increased Ca deposition in the bone and increase Ca excretion, both of which will decrease the [Ca2+].
How much of the filtered Ca2+ is reabsorbed by the kidney?
99%
Where is most of the phosphate in the body found?
Bone. 86% of it is stored in the bone.
How much of the Pi is normally reabsorbed in the PT?
80%. Pi is readily absorbed.
What is the effect of PTH on the Pi?
It increases the level of the plasma Pi and increases Pi excretion.
What is the effect of calcitriol on Pi?
It increases the level of the plasma Pi and decreases Pi excretion.
What is the effect of calcitonin on Pi?
It decreases the level of plasma Pi and increases Pi excretion.
