doing uworld qbank, got the next question: patient with a Conn syndrome and they ask us how renin, aldosterone and bicarbonate levels are in the blood....for renin and aldosterone is logic(renin low and aldosterone up); for bicarbonate, i thought it is low....why? since aldosterone will increase sodium retention but will increase potasium and hydrogen ion secretion, this will give a metabolic alkalosis(my logic was that at this moment the body will try to 'fix' the problem by not reabsorbing so much bicarbonate or at least to have normal values); on the explanation, they said because aldosterone gives a metabolic alkalosis, bicarbonate is high!!! the only problem is, in my opinion, this alkalosis is NOT due to increase level of bicarbonate but is due to increase secretion of hydrogen ion.
if anybody can help....thanks.

Hi,
This is how I solve this question. Hydrogen ion excretion is couple with bicarbonate re-absorption in proximal tubules. In excess of aldosterone, more sodium will re-absorb and more potassium and hydrogen ion will excrete that lead to relative excess of bicarbonate in the blood.

basicly , the bottom line in acid-base disturbances related to bicarbonate levels ......

in proximal n distal tubular cells,H2CO3 dissociates into bicarbonate n hydronium ion.and for each molecule of bicarbonate reabsorbed into the blood, one hydronium ion is secreated into the urine. in conn syndrome ,excess of aldosterone causes increased reabsorption of sodium which forces pottasium ion n hydronium ion into the urine by using soduim pottasium n sodium hydrogen pump respectively.and like i said earlier for each ion of hydronium secreated into the urine one molecule of bicarbonate is reabsorbed into the blood,thus producing the picture of metabolic alkalosis in conn syndrome.


hope dis will help

thank you very very much....this is the kind of explanation i was expected to get....now i got it....this is the real reason why we have exces bicarbonate in conn even though the syndrome produces alkalosis due to wasting hydrogen ion as the initial step and secondary gains bicarbonate; thanks to you i got the ideea; one more time thank you so much.

I've done Step one. Now, should I prepare for CK first, then CS? or CS first , and then CK? If I take CS first, do I forget the basic sciences of Step one required for CK?