| ABSTRACT: |
|
The potential inhibitory effects of phenethyl isothiocyanate (PEITC),
ellagic acid (EA), sulindac and supplemental dietary calcium (SDC) on
N-nitrosomethylbenzylamine (NMBA)-induced esophageal carcinogenesis were
evaluated in rats utilizing an abbreviated (5 week) NMBA treatment
protocol which allowed administration of the putative inhibitors
throughout the experiment (i.e. beginning 2 weeks prior to NMBA treatment)
or following completion of NMBA dosing only. PEITC at 500 p.p.m.
significantly inhibited tumor incidence and multiplicity when given before
and during, but not following, NMBA treatment. Neither sulindac at 125
p.p.m. nor SDC (2% versus 0.5% in control diet) inhibited tumor
development when given during or following NMBA treatment. EA, which was
administered only following NMBA treatment, significantly reduced the
incidence (66.7% versus 100% in NMBA controls), but not the multiplicity,
of esophageal tumors at the high-dose (4000 p.p.m.) level. Together these
findings indicate that: (i) PEITC selectively inhibits the induction but
not the subsequent progression of NMBA-induced esophageal tumors; (ii) EA
may repress esophageal tumor development when administered following NMBA
treatment; (iii) at the doses administered, neither sulindac nor SDC
possess significant inhibitory activity against NMBA-induced esophageal
carcinogenesis in the rat. |