Renal Sodium Balance Flashcards
What ion is most important in regulation of fluid content and body volume?
Sodium
Which segments of the nephron absorb sodium?
All except descending loop of henle
Which segment of the nephron filters to majority of sodium?
Proximal convoluted tubule - 65%
How is sodium reabsorbed in the proximal convoluted tubule?
- Co-transport with glucose, phosphate, amino acids
- Counter transport against hydrogen
- Diffusion
- Paracellular
What drives active transport of sodium in the proximal convoluted tubule?
Na/K ATPase on basolateral side
What regulates Na reabsorption in the proximal convoluted tubule?
Flow (GFR) & angiotensin II
How does angiotensin increase Na reabsorption
Increases activity of Na-H counter transporter
How is sodium reabsorbed in the thick ascending limb of the loop of henle?
Na-K-2Cl (NKCC) co-transporter-active transport
K is recycled, Cl becomes the limiting ion
How is sodium reabsorbed in the distal tubule?
Na-Cl co-transporter-active transport
How is sodium reabsorbed in the collecting duct?
ENaC epithelial sodium channels in principal cells
What are the effects of aldosterone in the collecting duct?
Increase sodium reabsorption by... 1. Increase activity of Na-K ATPase 2. Increase number of ENaC 3. Increase activity of ENaC Increase secretion of K and H
What are the effects of Atrial Natriuretic Peptide in the collecting duct?
Decrease Na reabsorption by …
- Increasing GFR
- Decrease activity of ENaC
What regulates sodium reabsorption in the proximal tubule?
Flow & Angiotensin II
What regulates sodium reabsorption in the ascending limb of the loop of henle?
Flow
What regulates sodium reabsorption in the distal tubule?
Flow
What regulates sodium reabsorption in the collecting duct?
Aldosterone & Atrial Natriuretic Peptide
How is sodium regulated by osmolality and tonicity?
It is not
What enzyme is responsible for converting angiotensin I to angiotensin II?
Angiotensin Converting Enzyme
What enzyme is responsible for converting angiotensinogen to angiotensin?
Renin
What are the consequences of increased angiotensin II?
- Increased thirst
- Increased vasopressin (ADH) release
- Increased systemic vasoconstriction
- Increased aldosterone release
What happens when intravascular volume drops?
Increased production of angiotensin II (proximal convoluted tubule) & aldosterone (collecting duct)
What hormones are released in response to intravascular volume increase due to dietary salt increase?
Atrial Natriuretic Peptide and Dopamine
On what transporter do loop diuretics exert their effects?
NKCC in the loop of henle - loop diuretics compete for the Cl binding site
Where do thiazide diuretics exert their effects?
Na-Cl co-transporter in the distal tubule
How much sodium is absorbed in the proximal convoluted tubule?
65%
How much sodium is absorbed in the ascending loop of henle?
25%
How much sodium is absorbed in the distal tubule?
5%
How much sodium is absorbed in the collecting duct?
5%
How does amiloride (potassium sparing diuretic) exert its effects?
Blocks ENaC in the collecting ducts preventing Na influx into the principal cell
