Distal Convoluted Tuble and NaCl and Ca

Prep for USMLE Forum

» Log in | Register

Forum

Step 1

Match

Prep4USMLE Forum » USMLE Step 1 Forum » Physiology Forum

Distal Convoluted Tuble and NaCl and Ca

Author

7 Posts

ticktock
Forum Newbie

Topics: 7
Posts: 8

09/20/07 - 03:14 PM

In the distal convoluted tubule, how does NaCl reabsorp affect Ca reabsorp? For example, how does hydrochlorothiazide's prevention of NaCl reabsorption decrease Ca urinary excretion? Thanks!

new_n_lost
Politically InCorrect
avatar

Topics: 652
Posts: 6,066

09/21/07 - 01:06 AM

There is a Na-Ca pump on the basolateral side of the tubule which pumps sodium in and calcium out into the blood. By decreasing the Concertration gradient of Na inside the DCT cell the sodium in the blood is pumped into the cell thereby decreasing the urinary calcium concerntration. As HCT blocks the NACl transport channels the difference in Concerntration gradient causes a shift in Calcium values.

___________________
FORUM RULES-- Those who believe in telekinesis, raise my hand. I get enough exercise just by pushing my luck --P4U World.." The pure and simple truth is rarely pure and never simple."

yuna
Forum Senior
avatar

Topics: 7
Posts: 229

09/21/07 - 04:53 PM

Just an image! thanks NNL for reminding

___________________
I have found my love...

new_n_lost
Politically InCorrect
avatar

Topics: 652
Posts: 6,066

09/21/07 - 05:15 PM

Yes I was looking for this picture cos its the best explanation there is for this question.

___________________
FORUM RULES-- Those who believe in telekinesis, raise my hand. I get enough exercise just by pushing my luck --P4U World.." The pure and simple truth is rarely pure and never simple."

ticktock
Forum Newbie

Topics: 7
Posts: 8

09/24/07 - 12:11 PM

Thanks for the replies. Based on the picture, it seems that if HCT were to block the NaCl cotransporter, there will be more Na in the DCT. Thus, Na in the blood will want to remain in the blood and by action of the Na/Ca antiport, Ca would want to remain in the DCT (increasing Ca excretion)? What am I missing here b/c HCT is supposed to decrease Ca excretion!

sfk
Forum Elite

Topics: 43
Posts: 294

09/24/07 - 05:52 PM

no, Na will not "want to remain" in blood, but will rather enter the DCT cell, & thence to the lumen. And as per the antiport, Ca would move from lumen to blood.

___________________
Forum Elite, But Step 2 Newbie....

new_n_lost
Politically InCorrect
avatar

Topics: 652
Posts: 6,066

09/24/07 - 05:52 PM

ticktock wrote:
Thanks for the replies. Based on the picture, it seems that if HCT were to block the NaCl cotransporter, there will be more Na in the DCT. Thus, Na in the blood will want to remain in the blood and by action of the Na/Ca antiport, Ca would want to remain in the DCT (increasing Ca excretion)? What am I missing here b/c HCT is supposed to decrease Ca excretion!

Plz read carefully all the replies before missing the point.

___________________
FORUM RULES-- Those who believe in telekinesis, raise my hand. I get enough exercise just by pushing my luck --P4U World.." The pure and simple truth is rarely pure and never simple."

You don't have permission to post.