Re: Sodium homeostasis...

J. Moore (
Wed, 1 Nov 95 10:31:00 -0500

Vi> J. Moore ( sez:

Vi> `The problem for the body, in terms of excreting of sodium (or
Vi> `potassium, etc.), is maintaining a balance (homeostasis) of water
Vi> `and sodium (or potassium, etc.). If an excreted solution has the
Vi> `same ratio of sodium to water as is in plasma, it doesn't change
Vi> `this balance, and the organ excreting this solution is not going
Vi> `to be able to rid the body of excess sodium. The solution itself
Vi> `is said to be isotonic. This is the situation with human tears.

Vi> `Human sweating excretes a substance which is hypotonic, having a
Vi> `lower ratio of sodium to water than is in plasma. Here too, the
Vi> `solution is not useful at ridding the body of excess sodium --
Vi> `quite the opposite -- since the body is eliminating proportionately
Vi> `more water than sodium from its plasma as it sweats.

Vi> Nevertheless, electrolyte loss through sweating is a problem, because
Vi> people drink fresh water to replenish their fluid loss, so the net
Vi> result is a constant fluid content, with fewer salts. Thus the advent
Vi> of electrolytically balanced drinks for athletes.
Vi> <== faster % Pete Vincent

And besides drinking fresh water, people eat things which contain
salts. Neither of these facts alter the fact that neither sweating
or tears are useful means of ridding the body of excess sodium,
and that this contrasts dramatically with the function of the
renal system, which produces hypertonic urine and is therefore
able to effectively rid the body of excess sodium.

Jim Moore (

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