Influence of acute exposure to heat on the blood-brain barrier permeability during acute hypertension.
In mild hyperthermic rats with acute hypertension induced by intravenous injection of adrenaline, changes in blood-brain barrier permeability to macromolecules were investigated using Evans blue as indicator. Evans blue albumin extravasation was determined macroscopically, and a quantitative estimation with spectrophotometer using homogenized brain to release the dye was also performed to evaluate the macroscopic findings. Four groups of rats were studied: group I: control normothermia; group II: acute exposure to heat; group III: normothermia + acute hypertension; group IV: acute exposure to heat + acute hypertension. The rats were anesthetized with diethyl-ether. Body temperature was increased by elevating ambient temperature in the vented box covered with a 3 mm thick black copper plate. The colonic temperature was increased to 39 +/- 0.5 degrees C. During adrenaline-induced acute hypertension the mean arterial blood pressure increased in both normothermic and mild hyperthermic animals. Mean values for Evans blue dye were found to be 0.20 +/- 0.04 mg% whole brain in normothermic control rats and 0.30 +/- 0.1 mg% in hyperthermic rats (p < 0.05). Mean values for Evans blue dye in the whole brain were found to be 0.63 +/- 0. 2 mg% in the normothermic rats and 0.40 +/- 0.2 mg% in the mild hyperthermic rats during adrenaline-induced hypertension (p < 0.05). Our results show that the extravasation of Evans blue albumin was less pronounced in the brains of mild hyperthermic rats compared to normothermic rats after adrenaline-induced acute hypertension.
Oztax427
Department of Physiology, Istanbul Faculty of Medicine, University of Istanbul, Turkey.
D000208:Acute Disease; D000818:Animals; D001794:Blood Pressure / Q000187:drug effects / Q000502:physiology; D001812:Blood-Brain Barrier / Q000502:physiology*; D001831:Body Temperature / Q000502:physiology; D004837:Epinephrine; D005070:Evans Blue; D006358:Hot Temperature / Q000009:adverse effects*; D006973:Hypertension / Q000139:chemically induced / Q000503:physiopathology*; D008297:Male; D051381:Rats; D017208:Rats, Wistar
D005070:Evans Blue; D004837:Epinephrine