Why is water homeostasis important?
What are baseline sodium and potassium in ECF?
Regulation of osmolarity
Sodium = 140 mEq/L
Potassium = 4 mEq/L
What are the two stimuli for ADH release?
What is the range of urine osm due to ADH?
Plasma osmolarity (increased Osm results in increased ADH)
Baroreceptor measurement of volume depletion (depleted volume results in increased ADH)
50 to 1200
What determins significance of hyponatremia?
What is the clinical manifestations of hyponatremia?
Prominent in rapid change in water
Non specific signs and symptoms (Nausea, vomiting, weakness, headache, siezure, RDS, death)
- What appropriately elevates ADH?
- What can result in excessive water intake?
- What cna result in altered renal water handling?
- What can cause inappropriate secretion of ADH?
- Volume depletion
- Hypotonic fluids, other irrigants
Cancer (small cell lung e.g.), CNS dz, Pul dz, Drugs (narcotics, antiemetics, SSRIs), HIV
What are the formula for creatinine clearance?
Creatinine Clearance = UCreat * UVol/(PCreat)
Cockcroft-Gault Estimate: Creatinine Clearance = ((140-age) * Weight (kg))/(Serum Cr * 72) * 0.85 (if female)
Creatinine clearance is always in mL/min
What is GFR? What is the range?
Amount of plasma filtered through glomeruli per unit time (90-125 mL/min)
What is the blood urea nitrogen?
How accurate of a GFR indicator is it?
What is it used for?
Nitrogenous waste product of protein metabolism
Less acrruate than creatinine due to variation in protein intake, catbolic rate, tubular reabsorption
Used to help diff dx with creatinine in renal dz
What is serum creatinine?
What can it be used to estimate?
Breakdown product of skeletal muscle
Production remains constant over time
Serum levels are inversely proportionate to GFR (~100/Cr)
What influences tubular Na reabsorption?
Renal sympathetic tone
What is the direct tubular effect of renal sympathetic nerves?
Of Angiotensin II?
Renal SNS - Multiple tubular receptors stimulate Na reabsorption
AngII - Tubular receptors, increases activity of the PT Na/H countertransporter
What is aldosterone's effect on Na reabsorption?
Stimulates Na reabsorption in cortical collecting duct principal cells
~2% of filtered load of Na has its excretion dependent on aldosterone action
Increases number of luminal Na channels and BL Na/K-ATPases
What controls aldosterone secretion?
Angiotensin II is most important stimulus relating to Na balance
What is the mechanism of action of ADH?
ADH binds to V2 which activates adenyl cyclase, increasing cAMP in the cell
cAMP leads to PKA cascade which leads to AQP2 insertion to the lumen of cell
AQP2 responsible for water reabsorption
What is the endocrine function of renin?
What is the endocrine function of erythropoietin?
What is the endocrine function of 1,25 dihydroxyvitamin D production?
Renin - Secreted by juxtaglomerular cells
Converts angiotensinogen to angiotensin, regulating BP and salt balance
Erythropoetin (epo) - Produced by renal cortical tubular cells, stimulates erythrocyte production in marrow
1,25-dihydroxyvitamin D - Formed in PT cells, regulates calcium and phosphate balance
What is the effect of CKD on calcium and parathyroid hormone?