This study was conducted to determine whether L-tryptophan binding to
nuclei of mt transplantable hepatomas (5123 and 19) differed from that
in host liver or normal liver of rats. Binding of L-tryptophan to rat
hepatic nuclear proteins has been demonstrated to be saturable, stere
ospecific, and of high affinity and the nuclear envelope binding prote
in has been purified and characterized. Using an in vitro H-3-tryptoph
an binding assay, the total and specific L-tryptophan binding was appr
eciably less in nuclei of hepatoma than in nuclei of host liver or nor
mal liver. On Scatchard analyses, the K-D values were similar for nucl
ei of hepatoma and of host liver but the B-max values were less in hep
atoma than in host liver. Free L-tryptophan levels and nuclear poly(A)
polymerase activity levels in hepatoma,were higher than those of host
liver. Using compounds (L-tryptophan implicated in the eosinophilia-my
algia syndrome, D,L-beta-(1-naphthyl)alanine, chlordiazepoxide, and 3-
methylindole) that had earlier been found to diminish in vitro H-3-try
ptophan binding to rat hepatic nuclei, similar inhibitory effects were
observed with nuclei of hepatoma or with nuclei of host liver. Using
polyclonal antibodies raised against the L-tryptophan binding protein
of Pat hepatic nuclear envelopes, immunoblot assay was performed on nu
clei of hepatoma and of normal liver. The receptor protein (67 kD) was
present in both preparations.