Effect of hypothermia on the intestinal absorption of uracil and L-dopa in the rat.
The in situ rat gut technique was used to explore the effects of hypothermia on the intestinal absorption of L-dopa and uracil. A hypothermic state was induced when male Sprague-Dawley rats, weighing between 300 and 370 g, were exposed to an atmosphere of helox (helium:oxygen, 80:20) at 0-4 degrees C. After 4 to 5 h, the rectal temperatures were decreased from 37 to 20 degrees C. The rewarming process for hypothermic animals undergoing anesthesia appears to be prolonged. The animals were prepared for surgery using ether as anesthetic after a rectal temperature of 20 degrees C was attained. Hypothermia showed a significant influence on decreasing L-dopa and uracil disappearances from the intestinal lumen. About 40 percent reduction of the rates of disappearance was observed with a 10 degrees C reduction of the rectal temperature. Additionally, a rapid drop of the rate of drug disappearance was observed in the beginning stage of rectal temperature decrease (31-36 degrees C) as well as in the hypothermic state with rectal temperatures < 26 degrees C. There appears to be a thermal stable region for absorption between 26 and 30 degrees C. Water efflux was studied in both normothermic and hypothermic animals. Normothermic rats showed greater average cumulative water efflux over a period of 30 min (71 and 61% for L-dopa and uracil, respectively) in comparison with that of hypothermic rats (34 and 41% for L-dopa and uracil, respectively). The cold-treated animals showed decreased rates of disappearance associated with the decreased water efflux. Therefore, the reduction of the rates of drug disappearance from the intestinal lumen caused by hypothermia may be partially related to the decrease of water efflux during hypothermia.
Stavchansky
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S
University of Texas at Austin, College of Pharmacy, Pharmaceutics Division 78712, USA.
Tung
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IL
D000818:Animals; D007035:Hypothermia / Q000378:metabolism*; D007408:Intestinal Absorption; D007980:Levodopa / Q000493:pharmacokinetics*; D008297:Male; D051381:Rats; D017207:Rats, Sprague-Dawley; D014498:Uracil / Q000493:pharmacokinetics*
D007980:Levodopa; D014498:Uracil