title: Transmembrane exchange of hyperpolarized 13C-urea in human erythrocytes: subminute timescale kinetic analysis.
abstract: The rate of exchange of urea across the membranes of human erythrocytes (red blood cells) was quantified on the 1-s to 2-min timescale. (13)C-urea was hyperpolarized and subjected to rapid dissolution and the previously reported (partial) resolution of (13)C NMR resonances from the molecules inside and outside red blood cells in suspensions was observed. This enabled a stopped-flow type of experiment to measure the (initially) zero-trans transport of urea with sequential single-pulse (13)C NMR spectra, every second for up to ~2 min. Data were analyzed using Bayesian reasoning and a Markov chain Monte Carlo method with a set of simultaneous nonlinear differential equations that described nuclear magnetic relaxation combined with transmembrane exchange. Our results contribute to quantitative understanding of urea-exchange kinetics in the whole body; and the methodological approach is likely to be applicable to other cellular systems and tissues in vivo.
authors.affiliation: Singapore Bioimaging Consortium, A(∗)STAR, Singapore.
authors.forename: Guilhem
authors.initials: G
authors.lastname: Pagès
authors.forename: Max
authors.initials: M
authors.lastname: Puckeridge
authors.forename: Guo
authors.initials: G
authors.lastname: Liangfeng
authors.forename: Yee Ling
authors.initials: YL
authors.lastname: Tan
authors.forename: Chacko
authors.initials: C
authors.lastname: Jacob
authors.forename: Marc
authors.initials: M
authors.lastname: Garland
authors.forename: Philip W
authors.initials: PW
authors.lastname: Kuchel
mesh_terms: D002247:Carbon Isotopes; D004910:Erythrocyte Membrane / Q000378:metabolism*; D006801:Humans; D007700:Kinetics; D026901:Membrane Transport Proteins / Q000378:metabolism; D008954:Models, Biological; D014508:Urea / Q000737:chemistry* / Q000378:metabolism*; D000096982:Urea Transporters
chemical_list: D002247:Carbon Isotopes; D026901:Membrane Transport Proteins; D014508:Urea; D000096982:Urea Transporters