Physio- Renal Regulation Of K+ & Ca2+ Flashcards
State the causes of Hyperkalemia (Shift of K+ out) in the cell.
- Insulin deficiency
- Acidosis
- B- antagonist
- Hyperosmolarity
- Excerice
- Cell lysis
- Inhibitors of the Na+-K+ pump.
State the causes of Hypokalemia (Shift of K+ in) in the cell.
- Insulin
- B- adrenergic agonist
- Alkalosis
- Hypoosmolarity
State the reabsorption rate of K+ in the Thick ascending limb of the loop of Henle.
What process is involved here?
—20%.
— Involves the Na+-K+-Cl- cotransporter.
Discuss the reabsorption of K+ in the Distal tubule and Collecting duct.
— Involves a H+, K+-ATP pump in the luminal membrane of the a- intercalated cells.
— only occurs in a low K+ diet due to the kidney trying to conserve as much K+ as possible.
Discuss the secretion of K+ in the Distal tubule and Collecting duct.
— K enters the basolateral membrane via the Na+-K+ pump
— K enters the lumen through passive transport via K+ channels.
— the magnitude of secretion of K+ depends on the chemical and electrical driving forces that pushes K+ in the luminal membrane.
— factors that increase intercellular [K] and decrease luminal [K], increase K+ secretion and the driving force
— factors that decrease intercellular [K], decrease the secretion and driving force.
State the significance of dietary K+ on secretion
A) A high diet of K+, increases intracellular K+, therefore causing an increase in K+ secretion.
B) A low diet of K+, decreases intracellular K+ and causing a decrease in K+ secretion.
State the significance of Aldosterone on K+ secretion.
— increases K+ secretion. (Hypokalemia)
— Mechanism involves Na being pushed out of the via the Na+-K+ pump. The pumping of Na+ out oyt the cell results in an increase in the uptake of K+ into the cell and increases intracellular K+, thus causing an increase in the secretion of K+
State the effects of Hyperaldosteronism and Hypoaldosternism.
— Hyperaldosteronism increases K+ secretion therefore causing Hypokalemia
— Hypoaldosteronism decreases K+ secretion therefore resulting hyperkalemia.
State the significance of Acid-base on K+ secretion.
— Acidosis — involves too much H+, therefore H+ enters the cell and K+ leaves the cell resulting in a decrease in intracellular K+ and secretion. (Hyperkalemia)
— Alkalosis — involves too little H+, therefore H+ leaves the cell and K+ enters the cell resulting an increase in intracellular K+ and secretion. (Hypokalemia)
State the significance of Loop and thiazide diuretics on K+ secretion.
— increases K+ secretion and caused Hypokalemia
— Loop and thiazide diuretics causes an increase in blood flow rate, thus causing a increase in the dilution of K+, increases the secretion
— Loop & thiazide also causes an increase in Na+ in the cell— pumping of Na+ out of the cell via the Na-K+ pump — increases intracellular K+ and secretion.
State the significance of K+ sparing diuretics on K+ secretion.
- Decrease in/inhibits K+ secretion. (Hyperkalemia)
- Decrease K+ excretion
- Increase K+ reabsorption.
Ex. Spironolactone, triamterene, amiloride.
Note: Inhibits Aldosterone.
State the significance of luminal anions on K+ secretion.
Increase in K+ secretion (Hypokalemia)
What is the significance of ADH on urea.
Stimulates a facilitated diffusion transporter for urea in the inner medullary collecting ducts.
What is the reabsorption rate of filtered phosphate in the proximal tubule?
85% by Na+ - phosphate cotransport.
Note: 15% is excreted because the distal nephron can’t reabsorb it.
What is the effect of parathyroid hormone on phosphate reabsorption?
— inhibits phosphate reabsorption.
— actives adenylate cyclase, generates cAMP, inhibits the Na+- phosphate cotransport.
— results in phosphaturia, increased urinary cAMP.
