AJP - Regulatory, Integrative and Comparative Physiology, Vol 256, Issue 5 1050-R1055, Copyright © 1989 by American Physiological Society
Regional alterations in hexokinase activity within rat brain during dehydration and rehydration
T. L. Krukoff and D. H. Vincent
Department of Anatomy and Cell Biology, Faculty of Medicine, University of Alberta, Edmonton, Canada.
Histochemical localization and photodensitometric quantification of the
metabolic enzyme, hexokinase (HK), were used to study changes in brain
metabolic activity that occur during the development of (5 days) and
recovery from (7 days) dehydration. In water-deprived (WD) rats, HK
activity increased after 2 days in the subfornical organ (SFO, 22%),
nucleus circularis (NC, 36%), parvo- and magnocellular divisions of the
paraventricular nucleus (pPVH, 17%; mPVH, 46%) and supraoptic nucleus (SON,
46%). Activity in SFO declined to control levels at 3 days but increased
again thereafter. In pPVH, mPVH, and SON, activity was elevated until the
end of the experiment. In NC, activity returned to control levels within 2
days of drinking by the rats. In salt-loaded (2% NaCl in water) rats,
changes were similar to those of WD rats up to 2 days of dehydration (SFO,
25%; NC, 20%; pPVH, 16%; mPVH, 38%; SON, 50%). Activity in SFO and pPVH
returned to control levels after 3 days and remained unchanged. In mPVH,
SON, and NC, activity remained elevated and declined to control levels when
salt-free water was provided. Results confirm that water deprivation is a
stronger dehydrating stimulus than salt loading. In addition, metabolic
activity, as measured by HK activity, varies daily during periods of
dehydration and rehydration. These changes cannot always be predicted from
results obtained only at the end of a period of dehydration. It is
concluded that it is necessary to study dehydration-induced changes in
brain metabolism on a daily basis to more fully understand the roles of
discrete brain regions in the regulation of body fluids.
