The purpose of the present study was to determine the minimal
arecaidine concentrations showing a synergistic effect on DMBA-induced hamster cheek pouch
carcinogenesis. One hundred and twelve male adult Syrian golden hamsters were divided into 16 groups, each containing seven animals. After eight weeks of DMBA initiation and then four weeks of
arecaidine promotion, 100%
tumor incidence was found with
arecaidine concentrations of 400 micrograms/ml and 500 micrograms/ml; average
tumor numbers were 1.86 +/- 0.63 and 1.86 +/- 0.93 respectively (P < 0.05). After four weeks of DMBA and a subsequent eight weeks of
arecaidine painting, all hamsters developed visible
tumors with
arecaidine concentrations
of 900 micrograms/ml and 1000 micrograms/ml; average
tumor numbers were 1.86 +/- 0.82 and 2.14 +/- 1.09 respectively (P < 0.05). The
tumor dimensions varied little and differences were not statistically significant. Without DMBA pretreatment, regardless of the high
arecaidine concentrations (1000 micrograms/ml, 2000 micrograms/ml and 3000 micrograms/ml) applied, no visible
tumor growth was observed; only hyperkeratosis and
inflammation could be discerned histologically. Thus, the minimal concentrations of
arecaidine displaying a synergistic effect in the DMBA-induced hamster cheek pouch of
carcinogenesis were found to be 400 micrograms/ ml applied for four weeks after eight weeks of DMBA application, and 900 micrograms/ml applied for eight weeks after four weeks of DMBA painting. These findings may be useful for other studies concerning the tumorgenicity of
arecaidine.