Detection of mutagenic activity in the urine of rodents treated with p-rosaniline

p‐Rosaniline was fed to male and female Fischer 344 rats and B6C3F1 mice at doses of 1,000 and 2,000 ppm for male rats and 500 and 1,000 ppm for female rats and mice of both sexes. Urine was collected overnight at 1‐wk intervals over a 4‐wk treatment period and frozen until its use in the mutagenicity assay. The neat urine was tested in triplicate without S‐9 on Salmonella tester strains TA98, TA100, TA1535, and TA1537 at 0.75, 0.5, 0.2, and 0.05 ml per plate. When sufficient urine was available, samples were tested on TA100 in the presence of S‐9. Either urine samples were pretreated for 18 hr at 37°C with β‐glucuronidase, or the deconjugating enzyme was added to the top agar at the time of plating in the mutagenicity assay (non‐pretreatment). Direct‐acting mutagenic activity was detected on TA98 in the urine from male mice, but only when using the non‐pretreatment deconjugation method. No direct‐acting mutagenic activity was detected in the urine of male and female rats and female mice; however, in the presence of S‐9, mutagenic activity was observed in the urine of male rats and in the urine of male and female mice regardless of the deconjugation method used. The non‐pretreatment method was superior for detecting direct acting mutagenic activity, and the pretreatment method was superior for detecting mutagenic activity requiring metabolic activation by S‐9.