Anions and Cations Flashcards
Acidemia results in what type of movement of K+?
From the ICF to the ECF
H+ ions are brought into the cell and exchanged for K+ ions
Alkalemia results in what type of movement of K+?
From the ECF to ICF
H+ ions are pushed out into the ECF; in exchange for K+ ions
What cells are primarily excreting K+ and reabsorbing K+ based on plasma levels?
K+ Reasborption: A-intercalated Cells
K+ Secretion: Principle cells
What is primary potential along the tubular lumen of the Collecting Duct?
Negative; - 50 mV
What are the characteristics and underlying etiology of Conn’s disease?
Conn’s Disease (Primary hyperaldosteronism)
- Aldosterone secreting tumor in the adrenal cortex
- K+ secretion in the collecting duct is innapropriately stimulated
- Consequence: Hypokalemia
What are the characteristics and underlying etiology of Addison’s Disease?
Addison’s Disease: Hypoaldosteronism
- Desctruction of Adrenal glands; aldosterone isn’t secreted
- Decreased K+ secretion in collecting duct
- Consequence: Hyperkalemia
What is the action of Osmotic Diuretics?
- Inhibit water reabsorption, and Na+, secondarily.
- Increased osmolarity of tubular fluid
- Act @ PCT
What is the action of Carbonic Anyhydrase inhibitors?
- Inhibit NaHCO3- reabsorption
- Can cause metabolic acidosis
- Act @ pCT
What is the action of loop diuretics?
- Inhibits Na+,K+, 2 Cl- cotransporter
- Increases RBF & decreased concentration of medullary intersitium
- Lessens water reabsorption at descending limb of Loop
- Acts @ Loop of Henle (20-25% of Na+ reabsorption)
What is the action of thiazide diuretics?
- Inhibit Na+/Cl- contransporter
- Increases Na+ secretion (primarily) and K+ secretion (secondarily)
- Decreased Ca2+ excretion
- Acts @ DCT
What is the action of K+ sparing diuretics?
- Inhibits Na+ reabsorption & K+ secretion
What is the concept of diuretic breaking?
- Chronic use of diuretics can lead to adaption of the distal sites to reabsorption the increased solute concentrations.
- Requires individuals take K+ supplements to prevent K+ wasting
What is the approximate % of total calcium that is filtered into Bowman’s capsule?
~ 55%
Where is the bulk of filtered Mg2+ reabsorbed?
It is reabsorbed via paracellular movement in the TAL; driving force is the positive transepithelial potential
What effect does insulin have on K+ regulation?
Also, what does diabetes mellitus cause in regards to K+?
1) It increases activity of Na+/K+ ATPase on the basolateral membrane of the principal cells; stimulating uptake of K+ into the cells
2) Associted with Hypokalemia
What do agonists of B2 adrengeric receptors cause in regards to K+?
They stimulate Na+/K+ ATPase; causing hypokalemia
What do agonists of A1 adrenergic receptors cause in regards to K+ reabsorption?
1) They cause shift of K+ out of the interstitum and into the pertibular capillary; causing Hyperkalemia
Where is Phosphate primarily reabsorbed?
PCT; via Na+/Phosphate cotransporter
What is the effect of PTH on Ca2+?
It increases its reabsorption of Ca2+ at the distal tubule, ; stimulating adenyl cyclase and cAMP, it also stimulates the production of Vit D3 (Calcitriol)
What is the effect of PTH on Phosphate?
It inhibits its reabsorption via; antagonist, of Na+/Phosphate cotransporter at the PCT
What two markers would be elevated as a result of increased PTH levels?
cAMP & Phosphaturia
What is Pseudohypoparathyroidism?
Defects in PTH’s receptor; Gs protein and Adenyl Cyclase –> Result: Renal cells are resistant to PTH
What are the main sites of Ca2+ reabsorption in the nephron?
1) Passive process; tightly coupled to Na+ reabsorption in the PCT and TAL
What classes of diuretics can treat hypercalciuria and hypercalcemia; respectively?
1) Treat Hypercalciuria: Increase reabsorption of Ca2+ –> Thiazide diuretics
2) Treat Hypercalcemia: Increase secretion of Ca2+ –> Loop diuretics
What is mechanism for increased Ca2+ reabsorption with Thiazide diuretics?
1) Inhibits Na+ reabsorption into cell via; Na+/Cl- contransport at DCT
2) Decreased intracelllular Na+ conc. (Interstitial fluid) –> Activates Na+/Ca+ exchanger
3) Ca2+ pumped out; Na+ pumped in
What is the mechanism for the secretion of Ca2+ with treatment via Loop diuretics?
1) Loop diuretics inhibit Na+/K+/ 2 Cl- pump @ TAL –> decreased K+ conc. Inside –> decrease K+ secretion to the tubular lumen
2) Potential becomes more negative –> Inhibits difffusion of Ca2+ into the cell
What effect does Loop diuretics have on Mg2+?
It increases its excretion
What cell of the distal tubule/collecting duct is primarily responsible for K+ reabsorption?
Intercalated Cell; via H+/K+ Exchange
What cell of the distal tubule/collecting duct is primarily responsible for secretion of K+ ?
Principal cells; leaky K+ channel
What is Conn’s disease?
Hyperaldosteronism
What is Addison’s disease?
HYpoaldosteronism
What is the generalized mechanism by which Loop diuretics inhibit NaCl reabsorption in the TAL of Henle?
They complete for chloride on the Na+/K+/ 2 Cl- cotranspoter
What is the main action of Vit D on Ca2+ reabsorption?
It increases Calbindin (Ca2+ carrier protein; which is responsible for its facilitated diffusion across the apical membrane)
What prevents paracellular reabsorption of Ca2+ in the distal tubule?
Tight junction protein Claudin-8 (CLDN8)
What is the mechanism for Ca2+ reabsorption in the TAL?
Positive lumen diffference; pushes Ca2+ paracellluarly –> into the interstitial tissue
What is the efffect of PTH & Calcitriol on Ca2+ levels?
They all stimulate reabsoprtion
What is the main efffect of Calcitonin on Ca2+ levels?
It prevents the osteoclastic reabsorption of bones; decreasing plasma Ca2+ level
How does PTH inhibit Phosphate reabsorption?
It lowers the Tm of Phosphate reabsorption at the Na+/Phosphate reabsorption at the PCT
Exercise generally causes what, regarding K+ conc?
Hyperkalemia
How does hypermagnesemia cause increased Ca2+ clearance?
It competes for reabsorption in the TAL
What is the major factor effecting Ca2+ reabsorption or secretion?
Na+ and water reabsorption; (Increased ECF Volume stimulates Ca2+ excretion)
