Elsevier

Advanced Drug Delivery Reviews

Volume 56, Issue 12, 14 October 2004, Pages 1811-1824
Advanced Drug Delivery Reviews

Confocal imaging of xenobiotic transport across the choroid plexus

https://doi.org/10.1016/j.addr.2004.07.010Get rights and content

Abstract

“You can see a lot by looking.”—Yogi Berra

Confocal microscopy is a tool by which the distribution of fluorescent compounds within living, complex tissues can be mapped at submicrometer resolution and quantitated. This laboratory has used confocal imaging and quantitative image analysis to visualize transport of xenobiotics across intact rat and mouse choroid plexus. For both organic anions and organic cations, transport from CSF to blood is a three-step process involving: uptake at the apical membrane of the epithelial cells, transcellular transport and efflux at the basolateral membrane. Both transmembrane steps are carrier-mediated and concentrative. In the cytoplasm of the epithelial cells, all fluorescent xenobiotics studied partition between diffuse and punctate compartments, some of which appear to be mobile. Use of confocal imaging in combination with transport inhibitors, treatments that alter metabolism and ion gradients and tissue from genetically altered mice, has allowed us to characterize transport at specific membrane sites and begin to identify the responsible transporters at the molecular level.

Section snippets

Transepithelial transport

Solute transport across a polarized epithelium, such as renal tubule or choroid plexus, involves three steps arranged in series. Solutes enter the cell at one side, traverse the cytoplasm and exit at the other side of the cell. The first and last steps, involving transport across functionally different regions of the plasma membrane, may be accomplished by simple diffusion, but solutes often receive help from one or more carrier proteins (transporters). Equilibrative transport across the

Xenobiotic transport across choroid plexus

One function of the choroid plexus is to remove potentially toxic xenobiotics and metabolic wastes from the cerebrospinal fluid (CSF). The capacity to do this can be seen from in vivo experiments in which xenobiotics injected into the ventricles of test animals are rapidly cleared to the blood and in vitro experiments in which isolated tissue rapidly accumulates and concentrates xenobiotics added to artificial CSF (aCSF) bathing the ventricular surface. The molecular basis for transport is a

Perspectives

Available evidence indicates that for both organic anions and organic cations the mechanisms underlying transepithelial transport are complex, involving specific transporters at both sides of the cells as well as intracellular sequestration by vesicles. Confocal microscopy and quantitative image analysis have only recently been applied to the study of xenobiotic transport mechanisms in choroid plexus. Yet it is already clear that these tools, when used in combination with more conventional

References (34)

  • D.H. Sweet et al.

    Organic anion transporter 3 [Slc22a8] is a dicarboxylate exchanger indirectly coupled to the Na+ gradient

    Am. J. Physiol.

    (2003)
  • Y. Nagata et al.

    Expression and functional characterization of rat organic anion transporter 3 (rOat3) in the choroid plexus

    Mol. Pharmacol.

    (2002)
  • D. Sykes, D.H. Sweet, S. Lowes, S.J. Nigam, J.B. Pritchard, D.S. Miller, Organic Anion Transport in Choroid Plexus From...
  • A.R.A. Villalobos et al.

    Transepithelial organic anion transport across shark choroid plexus

    Am. J. Physiol.

    (2002)
  • R. Masereeuw et al.

    Multiple pathways of organic anion secretion in renal proximal tubule revealed by confocal fluorescence microscopy

    Am. J. Physiol.

    (1996)
  • C.M. Breen et al.

    Fluorescein-Methotrexate Transport in rat choroid plexus analyzed using confocal microscopy

    Am. J. Physiol.

    (2004)
  • B. Noe et al.

    Isolation of a multispecific organic anion and cardiac glycoside transporter from rat brain

    Proc. Natl. Acad. Sci. U. S. A.

    (1997)
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