title: Promoting and anticarcinogenic effects of phenobarbital and DDT in the rat hepatocarcinogenesis.
abstract: The possible discrepancy between the dose level required for promoting action (when given after the initiation process, and that needed to exert an anticarcinogenic effect when given simultaneously with a carcinogen) of hepatic promoters were investigated in an attempt to obtain a "practical" threshold dose of promoters. Phenobarbital (PB) and dichlorophenyltrichlorethane (DDT) were used as promoters and 3'-methyl-4-(dimethylamino)-azobenzene (3'-Me-DAB) was used as the carcinogen. Male weanling rats were treated with either 600 ppm 3'-Me-DAB for 3 weeks followed by a diet containing a promoter at various dose levels (5-500 ppm), or the animals were treated with a low dose (100 ppm) of 3'-Me-DAB plus a promoter at various dose levels (20-500 ppm). The effects of promoters were measured by scoring size and number of enzyme-altered islands (EAIs) at 12 and 24 weeks of age. The promoting effect of PB and DDT was demonstrated in dose-dependent fashion, in the dose range of 10-500 ppm and 20-500 ppm, respectively. On the other hand, promoters given simultaneously with a low dose of carcinogen enhanced carcinogenesis at all the dose levels tested, in contrast with the inhibitory effect on carcinogenesis when given together with relatively high doses of carcinogens.
mesh_terms: D000818:Animals; D003043:Cocarcinogenesis; D003634:DDT / Q000633:toxicity*; D004347:Drug Interactions; D008114:Liver Neoplasms, Experimental / Q000139:chemically induced*; D008297:Male; D008749:Methyldimethylaminoazobenzene / Q000633:toxicity; D009152:Mutagenicity Tests; D010634:Phenobarbital / Q000633:toxicity*; D051381:Rats
chemical_list: D008749:Methyldimethylaminoazobenzene; D003634:DDT; D010634:Phenobarbital