Title

Indolic compounds affect tryptophan binding to rat hepatic nuclei

Document Type

Journal Article

Publication Date

1-1-1994

Journal

Journal of Nutrition

Volume

124

Issue

6

DOI

10.1093/jn/124.6.779

Abstract

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 (K(D)) under the two conditions, but the binding concentrations (B(max)) 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.

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