Response of rat selenoprotein P to selenium administration and fate of its selenium.
Selenoprotein P is a glycoprotein that contains greater than 60% of the selenium in rat plasma. Physiological experiments were undertaken to gain insight into selenoprotein P function. Selenium-deficient rats were injected with doses of selenium ranging from 25 to 200 micrograms/kg, and the appearance of selenoprotein P was compared with the appearance of glutathione peroxidase activity in plasma and in liver. Selenoprotein P concentration increased to 35% of control by 6 h, whereas glutathione peroxidase activity increased minimally or not at all. Moreover, in rats given 100 and 200 micrograms selenium/kg, selenoprotein P reached 75% of its concentration in control rats at 24 h, whereas glutathione peroxidase activity reached only 6% of control. Cycloheximide pretreatment blocked the appearance of selenoprotein P in response to selenium injection. Male and female rats had similar concentrations of selenoprotein P. Partially purified selenoprotein P and plasma glutathione peroxidase labeled with 75Se were administered intravenously to selenium-deficient and control rats. 75Se given as selenoprotein P disappeared more rapidly from plasma than did 75Se given as glutathione peroxidase. Selenium deficiency did not significantly affect 75Se disappearance from plasma. At 2 h, brain, but not other tissues, took up more 75Se in selenium-deficient rats than in control rats when 75Se was given as selenoprotein P. This suggests that brain has a specific uptake mechanism for selenium given in the form of selenoprotein P. These results demonstrate that several physiological properties distinguish selenoprotein P from glutathione peroxidase. However, they do not clearly indicate its function.
Burk
R F
RF
Department of Medicine, Vanderbilt University School of Medicine, Nashville, Tennessee 37232.
Hill
K E
KE
Read
R
R
Bellew
T
T
D000818:Animals; D004305:Dose-Response Relationship, Drug; D005260:Female; D005979:Glutathione Peroxidase / Q000378:metabolism; D006207:Half-Life; D007700:Kinetics; D009928:Organ Specificity; D014176:Protein Biosynthesis; D011506:Proteins / Q000378:metabolism* / Q000502:physiology; D051381:Rats; D011919:Rats, Inbred Strains; D012643:Selenium / Q000008:administration & dosage* / Q000378:metabolism* / Q000502:physiology; D051149:Selenoprotein P; D051140:Selenoproteins
D011506:Proteins; D051149:Selenoprotein P; D051140:Selenoproteins; D005979:Glutathione Peroxidase; D012643:Selenium