title: Influence of lead acetate and selected metal salts on tryptophan binding to rat hepatic nuclei.
abstract: This study evaluated whether lead acetate or other selected metal salts would influence the binding of L-tryptophan to rat hepatic nuclei. Lead salts and other salts of cadmium, zinc, mercury, and molybdenum, when added alone, had only small effects on 3H-tryptophan binding to hepatic nuclei in vitro. However, each of these salts, when added along with unlabeled L-tryptophan (excess, 10(-4) M), caused significantly less inhibition of 3H-tryptophan binding to hepatic nuclei than did unlabeled L-tryptophan alone. Lead acetate (10(-10) to 10(-4) M), when added along with unlabeled L-tryptophan, abrogated the inhibition of binding related to unlabeled L-tryptophan alone. Sodium arsenite (but not potassium arsenate) as well as sodium selenite (at 10(-4) M concentrations) inhibited to a moderate degree the in vitro 3H-tryptophan binding to hepatic nuclei, but addition of 10(-4) dithiothreitol, a protective agent for sulfhydryl groups, diminished this inhibition. Rats receiving a high dose of lead acetate before being tube-fed L-tryptophan displayed a decrease in hepatic protein synthesis compared with the stimulatory response connected with L-tryptophan alone. Thus, the addition of lead acetate and of other metal salts appears to have an inhibitory effect on L-tryptophan binding to hepatic nuclei. Lead acetate was investigated in in vivo experiments and was found to negate the stimulation of hepatic protein synthesis related to L-tryptophan alone.
authors.affiliation: Department of Pathology, George Washington University Medical Center, Washington, DC 20037, USA. pathxs@gwumc.edu
authors.forename: H
authors.initials: H
authors.lastname: Sidransky
authors.forename: E
authors.initials: E
authors.lastname: Verney
mesh_terms: D000818:Animals; D001667:Binding, Competitive / Q000187:drug effects; D002412:Cations / Q000633:toxicity; D002467:Cell Nucleus / Q000378:metabolism*; D004229:Dithiothreitol / Q000494:pharmacology; D004305:Dose-Response Relationship, Drug; D005260:Female; D008099:Liver / Q000187:drug effects* / Q000378:metabolism; D008670:Metals / Q000633:toxicity*; D009685:Nuclear Envelope / Q000378:metabolism; D009942:Organometallic Compounds / Q000633:toxicity*; D051381:Rats; D017207:Rats, Sprague-Dawley; D013439:Sulfhydryl Reagents / Q000494:pharmacology; D014316:Tritium; D014364:Tryptophan / Q000378:metabolism* / Q000494:pharmacology
chemical_list: D002412:Cations; D008670:Metals; D009942:Organometallic Compounds; D013439:Sulfhydryl Reagents; D014316:Tritium; D014364:Tryptophan; C008261:lead acetate; D004229:Dithiothreitol