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Old 05-28-2013
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Default Why alkalosis in loop & thiaziades

1)Can some1 plz explain Why alkalosis in Loop & thiazide diuretic and acidosis in k sparring??
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im not too sure but this is what i figured: loop and thiazide duiretics cause decrease in ECF volume and this leads to increased reabsorption of HCO3- (secondary to ecf volume contraction) => alkalosis

H+-K+ exchange in the distal tubule across the basolateral membrane. when u take K sparing diuretics [k] inside cell increases and this decreases the driving force. so more H+ in the blood = acidosis
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Quote:
Originally Posted by medicalbiology View Post
1)Can some1 plz explain Why alkalosis in Loop & thiazide diuretic and acidosis in k sparring??


ALdosterone effect: Reabsorb sodium inexchange for 'K , and H
i.e hypokalemia n alkalosis

so loop diuretic cause loss of Na cl h20 .compensatory response is aldosterone effect. (as above)

correct me if i am wrong plz
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Loop and HCTZ

Pee out a ton of water -> Lower ECF Volume -> Decreased renal perfusion -> Lower NaCl delivery to macula densa -> Increase in renin release and activation of Renin-Angiotensin-Aldosterone system

Activation of RAAS -> Increase ATII -> Increase in activity of Na+/H+ exchange in PCT -> More Na into cell, More H+ out. Remember that the source of this H+ is from carbonic anhydrase breakdown of H2CO3 into H+ and HCO3-. H+ goes one way into lumen, HCO3- has to go out the basolateral side where it is reabsorbed.

TL;DR: Low Blood Volume > increased Angiotensin II > increased Na/H exchange > contraction alkalosis

K+ Sparing

Aldosterone or the ENaC channels are blocked with these drugs so you can assume that it has an anti-aldosterone effect.

Recall that aldosterone was responsible for sodium reabsoprtion and potassium secretion from principal cells of the collecting duct.
Additionally, it increases H+ secretion from alpha intercalated cells.

Blocking this effect leads to H+ retention (less being secreted), and hence the acidosis

TL;DR: K+ sparing diuretics block effects of aldosterone > less H+ secretion from alpha intercalated cells > Metabolic acidosis
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