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64 Cards in this Set
- Front
- Back
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3 hormones produced from the kidney:
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-Active Vit D
-EPO -Renin |
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What does the kidney do to vitamin d?
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Hydroxylates it at the 1 position to produce 1,25 dihydroxyvitamin D3
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What is another name for 1,25 Dihydroxy D3?
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Calcitriol
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Where does Cholecalciferol come from?
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In the skin via UV activation
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Where does cholecalciferol get activated first?
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In the liver
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What is the product of liver action on inactive cholecalciferol?
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25-hydroxycholecalciferol
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25-hydroxycholecalciferol
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-Powerful feedback inhibitor of anymore liver activation
-Goes on to kidney for 2nd hydroxylation |
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Where in the kidney is vit D activated?
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Proximal tubule
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What stimulates activation of Vit D3 in the kidney?
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Decreased plasma calcium
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Where is calcium reabsorbtion stimulated by Vit D3?
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-Thick ascending limb
-Distal tubule -Intestinal epithelium |
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Where is EPO produced in fetal stages?
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Liver
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Where is EPO made after birth?
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In the kidney
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Main stimulus for EPO production:
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Tissue hypoxia
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What is lack of EPO the main cause of?
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Anemia associated with chronic renal failure.
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What is the effect of increased EPO?
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Increased red cell mass
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5 factors that stimulate EPO:
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-Pulmonary disease
-Anemia -Decreased hemoglobin -Decreased bloodflow -Decreased blood volume |
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Where is Renin found?
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In JG cells in the wall of the afferent arteriole.
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3 Major stimuli for Renin release:
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-Renal sympathetic nerve stimulation increase
-Decreased NaCl delivery to macula densa -Decreased renal perfusion pressure |
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2 hormones stimulated by renin:
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-Ang II (directly)
-Aldosterone (indirectly) |
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Where is aldosterone secreted?
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In the zona glomerulosa of the adrenal cortex.
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What important metabolic process is achieved by the kidney?
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Renal gluconeogenesis
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What does the kidney make glucose from? Where?
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Amino acids + lactate in the proximal tubule cells.
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When does renal gluconeogenesis become important?
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During periods of prolonged fasting.
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How much more glucose does the kidney produce relative to the liver during fasting?
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1/5
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What is the major amino acid substrate for the kidney's production of glucose?
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Glutamine
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What are the important byproducts of glutamine synthesis in the kidney?
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-NH4+
-HCO3 |
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What happens initially when a person takes a diuretic?
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-Sodium/H2O Excretion rate rapidly goes up and exceeds intake
-Intake stays the same -ECF volume goes down to 13 L |
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What happens in the 2-4 days after taking a diuretic?
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Na/H2O excretion rates go DOWN to once again match intake
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Why does excretion go down after taking a diuretic?
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Bc hormones kick in to increase Na/H2O reabsorption to increase ECF vol up to 14L
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How do osmotic diuretics work?
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By altering the osmotic driving forces along the nephron.
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How do osmotic diuretics alter the osmotic gradient?
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By increasing the osmolarity in the tubular lumen so water will go where the solute is - down the tube.
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Where do osmotic diuretics have their greatest effect?
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-Proximal tubule
-Thin desc LOH |
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What is the maximal effect of osmotic diuretics?
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Increased Na excretion to 10% of the filtered load.
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So how do osmotic diuretics change the osmotic gradient?
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They decrease it
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What is an exogenous osmotic diuretic?
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Mannitol
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How does the kidney handle mannitol?
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-Freely filtered
-Not reabsorbed -Trapped in tubular lumen |
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What are 2 endogenous osmotic diuretics? When are they clinically important?
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-Glucose - in uncontrolled diabetes mellitus
-Urea - in renal failure |
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What are the side effects of osmotic diuretics? (3)
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-Increased K excretion
-Incresed Bicarb excretion -Increased Ca excretion |
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How do the CA inhibitors work?
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-Inhibit CA
-Limit activity of Na/H exchanger -Decrease reabsorption of Na |
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Where is the major site of action of CA inhibitors? Why?
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Proximal tubules - predominant site of CA.
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What is the maximal effect of CA inhibitors?
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Increased Na excretion to 5-10% of the filtered load.
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What is a commonly used CA inhibitor?
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Acetazolamide
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Side effects of CA inhibitors:
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-Increased K excretion
-Incresed Bicarb excretion -Increased Ca excretion |
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What do loop diuretics target?
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Na/K/2Cl transporters in the thick ascending limb of LOH
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What is the effect of loop diuretics?
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Decreased Na reabsorption
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What is the major effect of inhibiting Na/K/2Cl transporter?
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Impairs kidney's ability to concentrate OR dilute urine by: 1. Preventing Na/Cl reabsorption from the tubule cell to blood
2. Preventing Mg/Ca reabsorption from the lumen to the tubule cell |
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Side effects of Loop diuretics:
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-Increased K excretion
-Increased Calcium excretion -Impaired ability to concentrate and dilute urine |
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3 common loop diuretics:
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-Furosemide
-Bumetanide -Ethacrynic acid |
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What is the maximum effect of loop diuretics?
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They acutely increase Na excretion up to 20% of the filtered load.
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Where do Thiazide diuretics work?
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In the early distal tubule
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What do Thiazide diuretics inhibit?
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Inhibit the Na/Cl Symporter in the Apical membrane of the early distal tubule.
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What is the maximum effect of the thiazide diuretics?
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They acutely increase Na excretion to 5-10% of the filtered load.
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What are 2 commonly used thiazide diuretics?
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-Chlorothiazide
-Metolazone |
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What are side effects of Thiazide diuretics?
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-Increased K excretion
-Decreased urinary diluting ability |
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Are thiazide diuretics as strong as Loop? Why/not?
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No because they're closer to the cortex and play less of a role in generating the medullary concentrating gradient.
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What is affected by loop diuretics that isn't by Thiazides?
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Ca excretion - this is coupled to the Na/K/2Cl transporter in TAL, but not in the distal tubule.
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How does making the early distal tubule cells impermeable to NaCl work as a diuretic?
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It decreases the kidney's ability to dilute urine
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Why are K-sparing diuretics called that?
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Bc they decrease sodium reabsorption AND K excretion.
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What is the target site of K-sparing diuretics?
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The principle cells of the late distal tubule and cortical collecting duct.
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What is the maximum effect of K-sparing diuretics?
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It increases sodium excretion to 3-5% of the filtered load.
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2 classes of K-sparing diuretics:
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-Aldosterone antagonists
-Na channel blockers |
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2 Aldosterone-antagonists:
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-Spironolactone
-Eplerenone |
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2 Na-channel blockers in principle cells:
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-Amelioride
-Triamterene |
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Side effects of K-sparing diuretics:
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-Decreased K excretion
-Increased bicarb excretion |
