Journal of Applied Physiology, Vol 64, Issue 6 2438-2443, Copyright © 1988 by American Physiological Society
Difference in rehydration process due to salt concentration of drinking water in rats
T. Okuno, T. Yawata, H. Nose and T. Morimoto
Department of Physiology, Kyoto Prefectural University of Medicine, Japan.
Albino rats were thermally dehydrated (approximately 8% of body wt),
divided into five groups, and given tap water or 0.2, 0.45, 0.9, or 2.0%
NaCl solution ad libitum for 16 h. Rats given 0.9 or 0.45% NaCl solution
regained fluid loss completely in 3-3.5 h, whereas those given 0.2%
solution became fully rehydrated at 10 h. The rats in the tap water and
2.0% NaCl groups were only 78 and 59% rehydrated, respectively, within 16
h. Na balance was positive in the 0.9% NaCl group by about five times the
amount of the cations lost during the dehydration period. A positive
balance of Na was also observed in the 0.45 (approximately 250%) and 2.0%
NaCl groups (300%), whereas the 0.2% NaCl group regained lost water and Na
simultaneously at 10 h. With tap water, additional loss of cations was
observed. These findings show that for the replacement of water due to
thermal dehydration there is a range of NaCl concentration with which the
rats can rehydrate with the mutual cooperation of thirst, salt appetite,
and kidney function.
