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THE SPECIFICITY AND SULFHYDRYL SENSITIVITY OF THE INOSITOL TRANSPORT SYSTEM OF THE CENTRAL NERVOUS SYSTEM
Author(s) -
Spector R.
Publication year - 1976
Publication title -
journal of neurochemistry
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.75
H-Index - 229
eISSN - 1471-4159
pISSN - 0022-3042
DOI - 10.1111/j.1471-4159.1976.tb01569.x
Subject(s) - choroid plexus , inositol , in vivo , blood–brain barrier , chemistry , biochemistry , choroid , biology , endocrinology , central nervous system , receptor , retina , neuroscience , microbiology and biotechnology
— The transport of two cyclohexitol stereoisomers, myo‐inositol (inositol) and scyllo‐inositol (scyllitol), from blood into the CNS in vivo and into the choroid plexus in vitro was studied. In vitro , the uptake of [ 3 H]scyllitol or [ 3 H]inositol by choroid plexuses, isolated from rabbits and incubated in artificial CSF, was measured. Both scyllitol and inositol inhibited [ 3 H]scyllitol or [ 3 H]inositol accumulation by the choroid plexus. Inositol competitively inhibited [ 3 H]scyllitol accumulation and both isomers had a comparable affinity (K t = 0.1 m m ) for the single cyclohexitol accumulation system. The other 6 stereoisomers tested had an order of magnitude less affinity for the cyclohexitol accumulation system of choroid plexus. Thiol reagents that penetrate cells inhibited inositol accumulation by choroid plexus more effectively than nonpenetrating thiol reagents. In vivo , in unanesthetized rabbits. the transport of unmetabolized [ 3 H]inositol from blood into CSF, choroid plexus and brain was readily saturated by increasing the plasma levels of myo‐inositol but not by the stereoisomer d ‐chiroinositol. Similarly, the transport of unmetabolized [ 3 H]scyllitol into CSF, brain and choroid plexus was readily saturated by increasing the plasma levels of myo‐inositol. Beside documenting the stereospecificity and thiol reagent sensitivity of the inositol transport mechanism of the choroid plexus, these results provide further evidence that the choroid plexus is a locus for cyclohexitol transport between blood and CSF. Moreover, they show that scyllitol, which, like inositol, is present at a higher concentration in brain than plasma, can be transported from blood into CSF and brain by the same system that transports inositol.