Electrolyte balance studies on rats maintained in metabolism cages - body fluid volume and electrolyte derangements by fasting in col

Brown, M. L.

Rogers, T. A.

Sather, B. T.

English

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. i' I ;. 
Terence A. Rogers, Ph,D., P r inc ipa l  Inves t iga to r  
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3. 
BODY FLUID VOLUME AND ELECTROLYTE DERANGEMENTS I N  FASTING 
Semi Annual Report #l, April ,  1965. 
Period covered by repor t .  
The grant  was ac t iva ted  October 1, 19C4. Ecpipnent was de- 
l i ve red  and s u i t a b l e  personnel were employed by Dsccmber l, 1964. 
This r epor t ,  therefore ,  covers research undertaken i n  a 4 month 
period of e f f e c t i v e  work between December 1, 1964 and March 31, 
19 65 . 
GPO PRICE $ 
Personnel engaged i n  t h e  research. 
OTS PRICE(S1 $ I 
The experiments conducted t o  d a t e  comprise a series of e lec t ro-  
l y t e  balance s tud ie s  on rats maintained i n  metabolism cages. These 
were primarily t o  determine whether t h e  rat, l i k e  man, continues t o  
l o s e  ur inary  sodium a t  t h e  onset of a f a s t  and whether t h i s  is  ex- 
acerbated by f a s t i n g  in t h e  cold. 
Figures 1 and 2 show t h e  sodium "balance" (Na i n t ake  - Urine 
Na) of f a s t i n g  rats kept a t  26' and 3OC. 
rat  d i e t  containing 20.26 mEq Na/100 g before  and a f t e r  t he  f a s t .  
The cont ro l  animals, who were fed throughout, show a s l i g h t l y  in- 
creased p o s i t i v e  sodium balance i n  t h e  cold. The negative so.diurn 
balance i n  rats f a s t i n g  a t  3' was considerably g r e a t e r  and t h e  sub- 
sequent r e t en t ion  of sodium upon refeeding was even more mar1:ed 
than i n  those f a s t i n g  a t  26OC. 
They were fed a standard 
Techniques are cu r ren t ly  being re f ined  i n  order  t o  study plasma 
volume, e x t r a c e l l u l a r  f l u i d  volume and t o t a l  body water i n  animals 
subjected t o  the  same regimens, 
A p a r t i c u l a r l y  i n t e r e s t i n g  aspec t  of t hese  r e s u l t s  is t h e  
s u b s t a n t i a l  magnesium excretion i n  t h e  cold,  by both fed  and f a s t ed  
rats, and the  sudden f a l l  of ur inary  magnesium excre t ion  upon re- 
tu rn  t o  t h e  warm (Fig. 3). Since t h i s  extra excre t ion  i s  seen i n  
both fed and f a s t ed  rats and is c u t  o f f  so promptly, i t  would appear 
t h a t  it might be a primary response t o  the cold and not  merely a 
r e f l e c t i o n  of increased gluconeogenesis. Further experiments on the  
magnesium economy of t h e  rat under these  conditions are already i n  
progress . 
It would be expected t h a t  t h e  sodium balance s t a t u s  of t h e  r a t  
p r i o r  t o  f a s t i n g  o r  cold exposure would a f f e c t  t h e  subsequent 
sodium losses.  
t o  f a s t i n g  and/or exposure t o  3OC d id  not show a s i g n i f i c a n t  nega- 
t i v e  sodium balance (Fig. 4). 
Rats fed a sodium-deficient d i e t  f o r  3 days p r i o r  
The weight loss during f a s t i n g  was 
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https://ntrs.nasa.gov/search.jsp?R=19650012530 2020-03-16T23:46:02+00:00Z
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loss in rats previously fed the sodium deficient diet than in those 
having received the normal diet; this is consistent with their 
maintenance of near sodium balance. 
however, showed an even more marked negative maznesium balance 
than those on a normal diet. 
theless, terminated just as abruptly on return to 26OC 
The "sodium depleted" rats, 
The magnesiun excretion was, ncver- 
(Fig. 5). 
4. Summary of work in progress. 
An elaborate series of 11 experiments is being conducted to 
investigate systematically the separate and additive effects of 
prior sodium status and prior ambient temperature exposure upon 
the sodium and magnesium losses during cold exposure and/or fast- 
ing. 
effects of fasting on sodium balance in the guinea pig. 
Preliminary experiments will be undertaken to determine the 
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Body fluid volume and electrolyte derangements in fasting semiannual report no. 1, dec. 1, 1964 - mar. 31, 1965

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