The oral LD50 for malachite green oxalate was found to be 275 mg/kg in rats while the approximate lethal dose for NMRI mice was 50 mg/kg. No systemic effects were seen after dermal application of 2,000 mg/kg. Repeated administration in the diet for 28 days to rats produced only minor changes in serum urea and aspartate aminotransferase levels. The rats at the highest dose level showed decreased weight gain and appeared clinically to have elevated motor activity. No sex differences were observed in either acute or prolonged experiments. In accord with human experience malachite green was irritating to mucous membranes, but no effects were seen on intact skin nor was it shown to be sensitizing. It was found to be a mutagen in the Salmonella/microsome test after metabolic activation but without clastogenic activity when tested at maximally tolerated levels in mice in the micronucleus test.

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Two potent cooked food mutagens, 2-amino-3-methylimidazo/4,5-f/quinoline (IQ) and 2-amino-3,4-dimethylimidazo/4,5-f/quinoline (MeIQ), were examined in an initiation-promotion assay in the male wistar rat. Fourteen doses of 10 mg IQ or 10 mg MeIQ/kg b.wt. were given during initiation, followed by promotion with 500 p.p.m. phenobarbital sodium (PB) in the drinking water up to week 58. A small number of tumours of Zymbal's gland were seen in all groups treated with IQ or MeIQ, irrespective of PB-treatment. Though the promotional regimen failed to produce the expected number of liver tumours, it did induce a significant amount of gamma-glutamyltranspeptidase (GGT) activity. These results suggest that even short exposures to low doses of IQ or MeIQ produce persistent procarcinogenic lesions in the rat, and that secondary factors, e.g. promoters or high cell turnover, may over time develop these lesions into cancer.