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Plasma, Cerebrospinal Fluid, and Brain Distribution of 14 C‐Melatonin in Rat: A Biochemical and Autoradiographic Study
Author(s) -
Vitte P. A.,
Harthe C.,
Lestage P.,
Claustrat B.,
Bobillier P.
Publication year - 1988
Publication title -
journal of pineal research
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.881
H-Index - 131
eISSN - 1600-079X
pISSN - 0742-3098
DOI - 10.1111/j.1600-079x.1988.tb00787.x
Subject(s) - cerebrospinal fluid , chemistry , pons , hypothalamus , endocrinology , melatonin , medicine , choroid plexus , central nervous system , biology
The distribution of 14 C‐Melatonin ( 14 C‐MT) after systemic injection was studied in the plasma, cerebrospinal fluid (CSF), and brain of rats. Chromatographic analysis (thin‐layer chromatography and high‐performance liquid chromatography) indicated that the radioactivity from biological samples taken at various times following the injection of label was mainly associated with 14 C‐MT. Computer analysis of plasma 14 C‐MT kinetics showed a three‐compartment system with half‐lives of 0.21 ± 0.05, 5.97 ± 1.11, and 47.52 ± 8.86 min. The volume of distribution and the clearance were 1,736 ± 349 ml. kg −1 and 25.1 ± 1.7 ml. min −1 . kg −1 respectively. The entry of 14 C‐MT into the CSF was rapid and reached a maximum at 5 min. The decay followed a two‐compartment system with half‐lives of 16.5 ± 2.9 and 47.3 ± 8.6 min. The CSF/plasma concentration ratio was 0.38 at the steady state (30 min). At 2 min the level of 14 C‐MT in the brain was 3.8 higher than in the CSF. Representative autoradiograms revealed an heterogeneous localization of 14 C‐MT in the grey matter. The highest regional values, as evaluated by the permeability area product technique, were found in cortex, thalamic nuclei, medial geniculate nucleus, anterior pretectal area, paraventricular nucleus of the hypothalamus, choroid plexuses, and bulb‐pons. Thirty minutes later 14 C‐MT was still detected in most of the brain regions analyzed. These results point to a low but rapid penetration of circulating MT into the brain and the CSF. The heterogeneous distribution and the partial retention of 14 C‐MT in the brain are compatible with the hypothesis of a central action of this hormone mediated via binding sites.