How does increased potassium intake lower blood volume?

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Spirochete
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I am confused about how increased potassium intake lowers blood volume. I understand that K+ is the primary intracellular cation, and Na+ is the primary extracellular one. I also know that the Na-K pump ejects 3 Na+ from the cell for every 2 K+ it brings into the cell.

My book physiology book is very vague about how this works. Anyone have an explicit explanation for how this works?
 

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I found this article that seems relevant (I haven't read the full article yet, just scanned the abstract):
http://www.sciencedirect.com/science?_ob=ArticleURL&_udi=B6WN4-4B3NCPD-M&_user=10&_rdoc=1&_fmt=&_orig=search&_sort=d&view=c&_acct=C000050221&_version=1&_urlVersion=0&_userid=10&md5=9cd76136713fee0969a58c9f181cfcc2

It looks like what potassium is doing is increasing the rate of sodium excretion, and it's really the shift in sodium that's reducing blood volume and thus blood pressure. I'm not completely sure on that though.
 
Hey thanks for looking around. I guessed that this would be something someone would know off the top of their heads, apparently it's more complicated than I'd thought. Sadly I don't have think I have access to ScienceDirect. I'll have to ask a professor whether I can access through my school.

I think you may have misread the abstract slightly, though. Were you referring to this sentence about sodium excretion?

"The fall in blood pressure was not related to urinary sodium excretion before entry to the trial or while on placebo."
 
Hmm...I think I pasted in the wrong link! I had two articles, one that referred to sodium excretion and was a more recent article, and one that was older and said it wasn't in their experiment. I think I got the older one but not the newer one if that's the quote you got from it. :confused:

This isn't even touched upon in my old books, so I'm guessing it's something added since I was in school, and I'm not finding it easy to locate research articles on it either. Since cardiovascular physiology isn't my specialty, I'd have to spend more time thinking through the whole system to try to reason through an explanation...might not do much better than you have on your own here. Maybe there's a reason the book is vague...sometimes it's because the authors don't know the mechanism either.
 
Yes that's probably my biggest pet peeve with science texts. I spend hours racking my brain trying to come up with an explanation for something, finally give up and ask a professor only to learn that nobody knows the answer. Or even if the answer is just too obscure/complicated to address in the text, the author could at least acknowledge that something isn't being explained adequately.

The article you're referring to might be there somewhere, I'm trying to navigate the cumbersome, giant fonted science direct website. . .
 
I think i have an explanation, Na is responsible for the osmotic force intravascularly ( as well as interstitially) urinary sodium excretion will led to lessened osmotic pressure and lowered blood pressure.