Hormonal influences on tryptophan binding to rat hepatic nuclei.
We evaluated whether selected hormones, 3,5,3'-triiodothyronine (T3), hydrocortisone (HC) or insulin, would influence the binding (saturable, stereospecific, and of high affinity) of L-tryptophan to rat hepatic nuclei or nuclear envelopes. T3 (10(-14) to 10(-10) M) appreciably inhibited in vitro L-(5-3H) tryptophan binding to hepatic nuclei and T3 (10(-16) to 10(-4) M) appreciably ameliorated the inhibitory effect of unlabeled tryptophan (10(-4) M) on such binding. In vivo tryptophan administration (1 h) stimulated hepatic protein synthesis but the addition of T3 negated such stimulation. HC (10(-12) to 10(-4) M) did not affect and insulin (10(-16) to 10(-4) M) had only a small inhibitory effect on 3H-tryptophan binding to hepatic nuclei, but each (10(-12) to 10(-4) M) when added to unlabeled tryptophan (10(-4) M) diminished the inhibitory binding effect of unlabeled tryptophan alone. Thus, T3 competes with tryptophan for hepatic nuclear tryptophan binding and also negates tryptophan's stimulatory effect on hepatic protein synthesis.
Sidransky
H
H
Department of Pathology, George Washington University Medical Center, Washington, DC 20037, USA.
Verney
E
E
D000818:Animals; D001665:Binding Sites; D001667:Binding, Competitive; D002467:Cell Nucleus / Q000187:drug effects / Q000378:metabolism*; D006728:Hormones / Q000494:pharmacology*; D006854:Hydrocortisone / Q000494:pharmacology; D007328:Insulin / Q000494:pharmacology; D007700:Kinetics; D008099:Liver / Q000378:metabolism*; D009685:Nuclear Envelope / Q000187:drug effects / Q000378:metabolism*; D051381:Rats; D014284:Triiodothyronine / Q000494:pharmacology; D014364:Tryptophan / Q000378:metabolism*
D006728:Hormones; D007328:Insulin; D014284:Triiodothyronine; D014364:Tryptophan; D006854:Hydrocortisone