Indolic compounds affect tryptophan binding to rat hepatic nuclei.
This study evaluates the effects of indolic or indole-related compounds on binding of L-tryptophan (saturable, stereospecific and of high affinity) to rat hepatic nuclei or nuclear envelopes. Addition of any one of many indolic or indole-related compounds, and particularly of 3-methylindole, does not inhibit in vitro binding of [3H]tryptophan to hepatic nuclear envelopes. However, when 3-methylindole (10(-10) to 10(-4) mol/L) is added in combination with unlabeled L-tryptophan (10(-4) mol/L), it diminishes the inhibitory effect of unlabeled L-tryptophan alone. Scatchard analysis of the binding affinities of in vitro [3H]tryptophan binding to hepatic nuclear envelopes using L-tryptophan in the absence or presence of 3-methylindole reveals similar dissociation constants (KD) under the two conditions, but the binding concentrations (Bmax) were greater in the combined group compared with that in the L-tryptophan alone group. Addition of 3-methylindole to liver before homogenization decreases specific [3H]tryptophan binding to nuclei compared with controls (without addition). L-Tryptophan tube-fed to rats with or without 3-methylindole administration increases in vitro hepatic protein synthesis compared with that of saline tube-fed controls. 3-Methylindole itself does not affect protein synthesis. Our report describes the effects of 3-methylindole on specific tryptophan binding to hepatic nuclear envelope receptor and discusses the possible implications thereof.
Sidransky
H
H
Department of Pathology, George Washington University Medical Center, Washington, DC 20037.
Verney
E
E
Cosgrove
J W
JW
Latham
P
P
Schwartz
A M
AM
D000818:Animals; D005260:Female; D007211:Indoles / Q000494:pharmacology*; D007930:Leucine / Q000378:metabolism; D008099:Liver / Q000187:drug effects* / Q000378:metabolism* / Q000648:ultrastructure; D008862:Microsomes, Liver / Q000187:drug effects / Q000378:metabolism; D009685:Nuclear Envelope / Q000187:drug effects / Q000378:metabolism; D014176:Protein Biosynthesis; D051381:Rats; D017207:Rats, Sprague-Dawley; D012862:Skatole / Q000494:pharmacology; D014364:Tryptophan / Q000378:metabolism*
D007211:Indoles; D014364:Tryptophan; D012862:Skatole; D007930:Leucine