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  • 1
    ISSN: 1432-1912
    Keywords: Human dental pulp ; Rabbit dental pulp ; Noradrenaline metabolism ; 6-Hydroxydopamine ; Uptake
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Abstract The study was undertaken to determine the relative roles of neuronal and extraneuronal uptake1 in the metabolism of 3H-noradrenaline in human dental pulp. Rabbit dental pulp was used as a reference since it was already known that normetanephrine (NMN) formation in this tissue utilised extraneuronal uptake,. Slices of pulp were preincubated in the absence and presence of 6-hydroxydopamine (1.6 mmol/l, for 10 or 20 min at pH 4.5) and subsequently incubated with 3H-noradrenaline (0.18 μmol/l for 30 min at pH 7.4). The principal metabolites formed were normetanephrine in rabbit pulp and deaminated catechols (dihydroxymandelic acid and dihydroxyphenylglycol) in human pulp. In both tissues 6-hydroxydopamine strongly inhibited formation of the deaminated catechols, but was without effect on normetanephrine formation. It is concluded that: i) in vitro 6-hydroxydopamine does not influence the metabolic process which is dependent on extraneuronal uptake1, namely normetanephrine formation in rabbit dental pulp, and in human pulp. Attention is drawn to an unusual feature of the neuronal metabolism in human pulp, namely the appearance of dihydroxymandelic acid as the principal metabolite.
    Type of Medium: Electronic Resource
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  • 2
    ISSN: 1432-1912
    Keywords: Rabbit dental pulp ; Ear artery ; Noradrenaline uptake ; Metabolism ; Cocaine
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Summary Incisor pulp from the rabbit metabolises exogenous noradrenaline in concentrations between 0.12 and 1.2 μmol/l mainly to NMN. Effects of chronic sympathetic denervation indicated that in incisor pulp the NMN is extraneuronal in origin, and that DOPEG and DOMA formation, as well as a major part of the noradrenaline which accumulates in the tissue, are associated with the sympathetic nerves. NMN formation was unaffected by hydrocortisone 210 μmol/l, but was strongly inhibited by cocaine 30 μmol/l. These effects contrasted with those in the rabbit ear artery, where NMN formation was increased by cocaine 30 μmol/l and decreased by hydrocortisone 210 μmol/l. In COMT-inhibited denervated pulp, cocaine inhibited the accumulation of noradrenaline. Monoamine fluorescence histochemistry of pulp exposed to noradrenaline 50 μmol/l indicated that cocaine-sensitive uptake occurred in fibroblasts. It is concluded that O-methylation of noradrenaline in dental pulp involves prior uptake of the amine by a process resembling uptake, but which is distinguished from uptake1 by its extraneuronal location.
    Type of Medium: Electronic Resource
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