Characterization of the irreversible inhibition of high-affinity choline transport produced by hemicholinium mustard.
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 nM (4-min incubation). A 10-min preincubation with 10 microM HCM results in essentially complete (greater than 95%) inactivation that persists after washing. Low-affinity choline transport in synaptosomes is unaffected by HCM inhibition at all concentrations examined (1-50 microM). Time course experiments indicate that the maximum irreversible inhibition (58%) seen after a 1-min preincubation with 500 nM 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.
Gylys
K H
KH
Department of Pharmacology, University of California School of Medicine, Los Angeles 90024.
Mellin
C
C
Amstutz
R
R
Jenden
D J
DJ
D000109:Acetylcholine / Q000037:antagonists & inhibitors; D000818:Animals; D001692:Biological Transport / Q000187:drug effects; D001921:Brain / Q000378:metabolism; D002794:Choline / Q000037:antagonists & inhibitors* / Q000378:metabolism; D006168:Guinea Pigs; D006426:Hemicholinium 3 / Q000031:analogs & derivatives*; D066298:In Vitro Techniques; D008297:Male; D009197:Myenteric Plexus / Q000378:metabolism; D051381:Rats; D017207:Rats, Sprague-Dawley; D013574:Synaptosomes / Q000378:metabolism
D006426:Hemicholinium 3; D002794:Choline; D000109:Acetylcholine