title: Evaluation of [14C] and [13C]Sucrose as Blood-Brain Barrier Permeability Markers.
abstract: Nonspecific quantitation of [14C]sucrose in blood and brain has been routinely used as a quantitative measure of the in vivo blood-brain barrier (BBB) integrity. However, the reported apparent brain uptake clearance (Kin) of the marker varies widely (∼100-fold). We investigated the accuracy of the use of the marker in comparison with a stable isotope of sucrose ([13C]sucrose) measured by a specific liquid chromatography-tandem mass spectrometry method. Rats received single doses of each marker, and the Kinvalues were determined. Surprisingly, the Kinvalue of [13C]sucrose was 6- to 7-fold lower than that of [14C]sucrose. Chromatographic fractionation after in vivo administration of [14C]sucrose indicated that the majority of the brain content of radioactivity belonged to compounds other than the intact [14C]sucrose. However, mechanistic studies failed to reveal any substantial metabolism of the marker. The octanol:water partition coefficient of [14C]sucrose was >2-fold higher than that of [13C]sucrose, indicating the presence of lipid-soluble impurities in the [14C]sucrose solution. Our data indicate that [14C]sucrose overestimates the true BBB permeability to sucrose. We suggest that specific quantitation of the stable isotope (13C) of sucrose is a more accurate alternative to the current widespread use of the radioactive sucrose as a BBB marker.
authors.affiliation: Department of Pharmaceutical Sciences, School of Pharmacy, Texas Tech University Health Sciences Center, Amarillo, Texas 79106.
authors.forename: Mohammad K
authors.initials: MK
authors.lastname: Miah
authors.affiliation: Department of Pharmaceutical Sciences, School of Pharmacy, Texas Tech University Health Sciences Center, Amarillo, Texas 79106; Center for Blood-Brain Barrier Research, School of Pharmacy, Texas Tech University Health Sciences Center, Amarillo, Texas 79106.
authors.forename: Ekram A
authors.initials: EA
authors.lastname: Chowdhury
authors.affiliation: Department of Pharmaceutical Sciences, School of Pharmacy, Texas Tech University Health Sciences Center, Amarillo, Texas 79106; Center for Blood-Brain Barrier Research, School of Pharmacy, Texas Tech University Health Sciences Center, Amarillo, Texas 79106. Electronic address: ulrich.bickel@ttuhsc.edu.
authors.forename: Ulrich
authors.initials: U
authors.lastname: Bickel
authors.affiliation: Department of Pharmaceutical Sciences, School of Pharmacy, Texas Tech University Health Sciences Center, Amarillo, Texas 79106; Center for Blood-Brain Barrier Research, School of Pharmacy, Texas Tech University Health Sciences Center, Amarillo, Texas 79106; Department of Biomedical and Pharmaceutical Sciences, Chapman University, School of Pharmacy, Irvine, California 92618. Electronic address: mehvar@chapman.edu.
authors.forename: Reza
authors.initials: R
authors.lastname: Mehvar
mesh_terms: D000818:Animals; D001812:Blood-Brain Barrier / Q000378:metabolism*; D002199:Capillary Permeability; D002247:Carbon Isotopes / Q000008:administration & dosage / Q000493:pharmacokinetics; D002478:Cells, Cultured; D008297:Male; D051379:Mice; D017207:Rats, Sprague-Dawley; D013395:Sucrose / Q000008:administration & dosage / Q000493:pharmacokinetics*
chemical_list: D002247:Carbon Isotopes; D013395:Sucrose
keywords: [(13)C]sucrose; [(14)C]sucrose; apparent brain uptake clearance; blood-brain barrier permeability