| Summary: | BACKGROUND: Phenolphthalein was formerly used as a laxative. Phenolphthalein is known to cause cancer in rats and mice. We tested phenolphthalein in a genetically modified mouse strain that lacks two tumor suppressor genes as part of a study to determine if this mouse model could detect cancer-causing chemcals more rapidly than the standard 2-year rodent bioassay. METHODS: We gave groups of 15 male or 15 female haploinsufficient p16Ink4a/p19Arf mice feed containing phenolphthalein for 27 weeks. The concentrations were 200, 375, 750, 3,000 or 12,000 parts per million (ppm) of phenolphthalein; other animals receiving untreated feed served as the control groups. Tissues from 22 organs were examined for every animal. RESULTS: Exposure to phenolphthalein caused atrophy of the testes, reduction in spermatids, and kidney nephropathy and hypertrophy in male haploinsufficient p16Ink4a/p19Arf mice and hyperplasia of the thymus and hematopoietic cell proliferation of the spleen in male and female haploinsufficient p16Ink4a/p19Arf mice. However, there were no increased incidences of cancer in the exposed animals. CONCLUSIONS: We conclude that phenolphthalein did not cause cancer in male or female haploinsufficient p16Ink4a/p19Arf mice, although it has in some other strains of mice and in rats. Phenolphthalein did cause atrophy of the testes and nephropathy and hypertrophy of the kidney in male haploinsufficient p16Ink4a/p19Arf mice and hyperplasia of the thymus and hematopoietic cell proliferation of the spleen in male and female haploinsufficient p16Ink4a/p19Arf mice
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