© 1995 American Heart Association, Inc.
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Hormonal Dependence of the Effects of Metabolic Encephalopathy on Cerebral Perfusion and Oxygen Utilization in the Rat
From the Neuroradiology Section, University of California at San Francisco (E.K., T.P.L.R., Z.S.V., J.K.); the Department of Clinical and Applied Physiology, School of Medicine, Warsaw, Poland (E.K., M.O.); and the Department of Medicine, Geriatrics Section, Veterans Affairs Medical Center and University of California at San Francisco (A.I.A.).
Correspondence to Allen I. Arieff, MD, Department of Medicine, V.A. Medical Center (111G), 4150 Clement Street, San Francisco, CA 94121.
Abstract Previous studies have demonstrated that in adult rats with chronic hyponatremia, both symptoms of encephalopathy and mortality largely depend upon the gender of the animal and the presence of elevated plasma levels of vasopressin (AVP). Since effects of AVP on blood vessels may be gender dependent, the present study was designed to compare the effects of chronic (4 days) hyponatremia on cerebral blood flow (CBF), cerebral oxygen consumption (CMRO2), and cerebral perfusion index (CPI) in adult male and female rats. CBF (intra-arterial 133Xe injection method) and CMRO2 (arteriovenous difference of cerebral oxygen contentxCBF) were measured in normonatremic and hyponatremic (hyponatremia induced with 140 mmol/L glucose and either AVP or desmopressin [dDAVP], plasma sodium=100 to 110 mmol/L) adult rats of both genders. The CPI was assessed from magnetic resonance imaging of the transit of magnetic susceptibility contrast agent through the brain. Female rats with AVP-induced chronic hyponatremia had a 36% decrease in CBF and a 60% decrease in CMRO2. In male animals, both parameters were not different from control values. AVP-induced hyponatremia resulted in a 45% decrease in CPI in female rats, but hyponatremia induced with dDAVP did not affect CPI in either male or female rats. Chronic (4 days) administration of AVP did not affect CPI in either male or female normonatremic rats. When rats with AVP-induced chronic hyponatremia were pretreated with estrogen, the CPI in males was not different from that in females. Our results demonstrate that during AVP-induced chronic hyponatremia in female rats, there is significant depression of both oxygen utilization and blood flow in the brain.
Key Words: cerebral blood flow • hyponatremic encephalopathy • vasopressin • estrogen • hyponatremia • brain oxygen utilization
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