Renegade
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Could someone plz explain by which mechanism is Ca excretion increased by hypernatremia? And how is oxalate stone formation favoured by urate-rich environment?... 
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| smal
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Ca is abs from the same channels as is Na in PCT which are PTH dependent.
so if Na is being abs,there will be hypocalcaemia.same whn we use thiazides,we r inhibiting Na abs. so channels are free to abs Ca from glomerular filterale.notice Na is more imp for boday so noramlly ,its abs will exceed Ca abs.
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| Leopard
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Dear Renegade
Look at Ca++ reabsorption as parallel companion of Na in
- Proximal convoluted tubule
- Thick asending limb
If Na is reabsopbe ,Ca is reabsorbed
If Na is retained in lumen ,Ca is retained in the lumen
And ,do not forget that
IN PCT = 67%
IN THICK ascending LImb = 25%
of Na and Ca reabsorption occurs.That is the reason in Hypecalcemia our first strategy to get rid of Ca is
- Hydration of the patient = Hypervolemia decreases reabsorption of Na ,thus Ca from PCT
- Loop Diuretic = More excretion of Na and Ca
Forget about PTH dependent Ca reasorption in the Early Distal convoluted tubule.
As far as your second part of quetion is concerned ,Urate precipitation acts as a nidus for Ca oxalate precipation as (in analogy) primer acts for DNA replication or Glycogenin acts for Glycogen synthesis .
Best of luck
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| Renegade
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Thnx a lot, I won't forget now
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«The desire to take medicine is perhaps the greatest feature which distinguishes man from animals.» W. Osler
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| Renegade
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Wait wait wait.
But tiazide diuretics are part of tx for hypercalciuria. By inhibiting Na reab., won't more calcium go to urine and favour formation of stones?
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«The desire to take medicine is perhaps the greatest feature which distinguishes man from animals.» W. Osler
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| Leopard
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That is true.Actually these are different channels in Eary distal convoluted tubules.I have talked about only PCT and TAL.
No doubt in the early DCT thiazide cause reabsorption of Ca thus reducing Ca excretion.
Loop diuretics -----------> Ca excretion
Thiazide diuretics ----------> Ca Re-absorption
Action of thiazides is not throught manipulation of Na, it is an independent action ,while that of Loop diuretics is through manipulation of Na excretion.
Best of luck
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FA is just a good revision book.It is not a "real" learning tool.
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