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Characterization of the Irreversible Inhibition of High‐Affinity Choline Transport Produced by Hemicholinium Mustard
Author(s) -
Gylys Karen Hoppens,
Mellin Charlotte,
Amstutz René,
Jenden Donald J.
Publication year - 1992
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.1471-4159.1992.tb08441.x
Subject(s) - choline , acetylcholine , incubation , chemistry , myenteric plexus , potency , biochemistry , synaptosome , guinea pig , in vitro , biophysics , pharmacology , biology , medicine , endocrinology , immunohistochemistry
The inhibition of high‐affinity choline transport by hemicholinium mustard (HCM), an alkylating analogue of hemicholinium‐ 3 , was examined in rat brain synaptosomes and guinea pig myenteric plexus. In synaptosomes, 50% high‐affinity choline transport inhibition occurs with an HCM concentration of 104 n M (4‐min incubation). A 10‐min preincubation with 10 n M HCM results in essentially complete (>95%) inactivation that persists after washing. Low‐affinity choline transport in synaptosomes is unaffected by HCM inhibition at all concentrations examined (1–50 μ M ). Time course experiments indicate that the maximum irreversible inhibition (58%) seen after a 1‐min preincubation with 500 n M HCM decreases to 46% inhibition after a 15‐min preincubation; however, analysis of variance reveals that this difference is not significant. HCM inhibition of acetylcholine release from myenteric plexus‐longitudinal muscle preparations persists for at least 2 h after removal of drug from the incubation bath; this inactivation can be prevented by coincubation with a high choline concentration during treatment with the mustard. In contrast, inhibition produced by the parent compound hemicholinium‐3 is largely reversed by washing in both preparations : examined. The observed potency and selectivity of HCM suggest its usefulness as a covalent probe for high‐affinity choline transport.