Relationship of membrane-bound sulfhydryl groups to vitamin D-stimulated uptake of [75Se]Selenite by the brush border membrane vesicles from chick duodenum.
The uptake of selenite by purified brush border membrane vesicles isolated from duodena of rachitic or vitamin D-treated chicks was studied by using radioactive selenite and a rapid filtration technique. Cholecalciferol treatment (500 IU at 72 h) significantly enhanced selenite uptake, a response that decreased when the vesicles were stored at room temperature for 2.5 h prior to the uptake measurement. Preincubation of the vesicles in 1.0 mmol/L H2O2 reduced [75Se]selenite uptake, indicating the involvement of oxidizable groups in the uptake reaction. Iodoacetic acid (IAA), a sulfhydryl-blocking reagent, at 1-2 mmol/L concentration eliminated the difference in selenite uptake due to cholecalciferol and had no effect on vesicles from rachitic animals. A higher concentration of IAA (10 mmol/L) enhanced selenite uptake manyfold and increased the absolute difference due to cholecalciferol treatment. Single intravenous doses of 100 IU cholecalciferol, 100 IU ergocalciferol, or 0.1 micrograms 1,25-dihydroxycholecalciferol also stimulated selenite uptake, suggesting a general response to vitamin D compounds. Normal animals given a single dose of 1,25-dihydroxycholecalciferol 12 h prior to killing also responded. Treatments that enhanced the uptake of [75Se]selenite also increased the amount of membrane-bound sulfhydryl groups, suggesting the involvement of membrane-bound sulfhydryl groups in the vitamin D response. A significant increase in selenite uptake by intravenous 1,25-dihydroxycholecalciferol occurred within 10 min. This rapid effect provides a new tool to probe early biochemical effects of vitamin D on intestinal epithelium.
Mykkanen
H M
HM
Department of Physiology, New York State College of Veterinary Medicine, Cornell University, Ithaca 14853.
Wasserman
R H
RH
D000818:Animals; D002117:Calcitriol / Q000494:pharmacology; D002645:Chickens; D002762:Cholecalciferol / Q000494:pharmacology; D004386:Duodenum / Q000187:drug effects / Q000378:metabolism*; D004872:Ergocalciferols / Q000494:pharmacology; D006861:Hydrogen Peroxide / Q000494:pharmacology; D007461:Iodoacetates / Q000494:pharmacology; D019807:Iodoacetic Acid; D007700:Kinetics; D008297:Male; D008871:Microvilli / Q000187:drug effects / Q000378:metabolism*; D012279:Rickets / Q000378:metabolism; D020887:Selenious Acid; D012643:Selenium / Q000378:metabolism*; D012644:Selenium Radioisotopes; D013438:Sulfhydryl Compounds / Q000378:metabolism*; D014807:Vitamin D / Q000494:pharmacology*
D004872:Ergocalciferols; D007461:Iodoacetates; D012644:Selenium Radioisotopes; D013438:Sulfhydryl Compounds; D014807:Vitamin D; D002762:Cholecalciferol; D006861:Hydrogen Peroxide; D020887:Selenious Acid; D002117:Calcitriol; D012643:Selenium; D019807:Iodoacetic Acid