title: Multiple specific binding targets for inhaled anesthetics in the mammalian brain.
abstract: Previous work showed widespread saturable binding of halothane in rat brain. To determine whether this represents selective binding to a few widespread proteins or less selective binding to many different proteins, we used [(14)C]halothane photolabeling and quantitative electrophoresis/autoradiography in rat cerebellar homogenates. Many proteins incorporate label. Stoichiometry values ranged from 0 to 4 at 0.2 mM [(14)C]halothane in a group of 24 randomly selected protein bands. Apparent IC(50) values from unlabeled halothane competition experiments ranged from 0.2 to 2.0 mM, with soluble protein having significantly lower values (higher affinity) than membrane protein. Chloroform inhibited halothane labeling similar to unlabeled halothane but with higher apparent IC(50) values, whereas isoflurane and an anesthetic, cyclobutane (1-chloro-1,2,2-trifluorocyclobutane), inhibited halothane labeling to a smaller degree. A nonanesthetic, cyclobutane (1,2-dichlorohexafluorocyclobutane), inhibited halothane labeling the least. We conclude that halothane binding motifs are sufficiently degenerate to be found in many proteins, both soluble and membrane-bound.
authors.affiliation: Department of Anesthesia, University of Pennsylvania, Philadelphia, Pennsylvania 19104, USA.
authors.forename: Maryellen Fazen
authors.initials: MF
authors.lastname: Eckenhoff
authors.forename: Kin
authors.initials: K
authors.lastname: Chan
authors.forename: Roderic G
authors.initials: RG
authors.lastname: Eckenhoff
mesh_terms: D018685:Anesthetics, Inhalation / Q000378:metabolism*; D000818:Animals; D001345:Autoradiography; D001665:Binding Sites / Q000187:drug effects; D001921:Brain / Q000378:metabolism*; D002531:Cerebellum / Q000187:drug effects / Q000378:metabolism; D004591:Electrophoresis, Polyacrylamide Gel; D066298:In Vitro Techniques; D008297:Male; D008565:Membrane Proteins / Q000378:metabolism; D008970:Molecular Weight; D019920:Photoaffinity Labels; D011485:Protein Binding; D051381:Rats; D017207:Rats, Sprague-Dawley
chemical_list: D018685:Anesthetics, Inhalation; D008565:Membrane Proteins; D019920:Photoaffinity Labels