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Kinetics of Choline Uptake into Isolated Rat Forebrain Microvessels: Evidence of Endocrine Modulation
Author(s) -
Shimon Mazal,
Egozi Yakov,
Kloog Yoel,
Sokolovsky Mordechai,
Cohen Sasson
Publication year - 1988
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.1471-4159.1988.tb02469.x
Subject(s) - choline , endocrinology , medicine , incubation , forebrain , chemistry , biology , biochemistry , central nervous system
The active uptake of [methyl‐ 3 H]choline into isolated rat brain microvessel suspension was studied as a likely guide to the transport of choline across the blood‐brain barrier. The method consisted primarily of incubation of the suspension with a fixed concentration of labeled choline in the presence of increasing concentrations of un‐labeled choline or any other inhibitor (I) of active uptake, denned as the difference in uptake at 37° and 0°C. From the linear regression of (1/V) against [I], the following values of K max (nmol g −1 min −1 ) and K m (μM ) were obtained for choline: 2‐month‐old males, 10.6 ± 3.8 and 6.1 ± 0.9; 3‐month old random females, 28.4 ± 5.9 and 12.6 ± 4.0; females at metaestrus, 17.8 ± 10.3 and 8.3 ± 5.0; at diestrus, 31.1 ± 9.3 and 13.0 ± 2.6; at proestrus, 54.9 ± 2.2 and 14.0 ± 1.5; at estrus, 19.2 ± 2.2 and 2.6 ± 1.7. The differences between males and random females (p < 0.018) and between females at proestrus and estrus (p < 0.005) are significant. It is suggested that these inter‐ and intrasex variations in choline uptake reflect a dynamic adjustment of supply in accordance with brain demand for choline at the time of assay. Hemicholinium‐3 was an effective inhibitor of choline uptake, K i = 14.0 ± 8.5 μ M; dimethylaminoethanol was much less effective; and imipramine had no measurable effect.