Effect of diet on fecal excretion and gastrointestinal tract distribution of unmetabolized benzo(a)pyrene and 3- methylcholanthrene when these compounds are administered orally to hamsters.

3-Methylcholanthrene (3MC) administered p.o. has induced tumors of the hamster gastrointestinal tract (GIT), including the large intestine. This process may depend on the concentration of unchanged hydrocarbon in the GIT contents. Benzo(a)pyrene (BP) ingestion could be involved in human GIT carcinogenesis. Accordingly, male Syrian golden hamsters were fed diets containing BP or 3MC for 10 days. Feces collected during the last two to three days of feeding were analyzed for the unchanged hydrocarbons by KOH:methanol digestion, Florisil column and paper chromatography, and ultraviolet spectrophotometry. With a semisynthetic diet containing 5% Alphacel, 6% corn oil, and 100 microgram BP per g. fecal BP excretion was 0.45% of the dose. Variation of the corn oil content had little effect. Fecal BP excretion was increased 13 times (to 6% of the dose) when 5% wheat brain was used in place of Alphacel and 4.5 times when a commercial diet was used. This suggests that bran adsorbed or sequestered the BP. Water content of the large-intestine contents was increased when the brain diet was fed. Both these factors could affect mucosal exposure to BP. For 3MC, fecal excretion of unchanged hydrocarbon was 14 times greater than for BP under similar conditions. The GIT contents of hamsters fed BP or 3MC showed hydrocarbon concentrations in the order: stomach greater than lower large intestine greater than other sections.

A carcinogenicity study of pesticide dieldrin in hamsters.

Syrian golden hamsters were fed for their lifespan a diet containing 0, 20, 60 and 180 parts per million (ppm) Dieldrin. Tumour-bearing animals totaled 13% among control females and ranged between 3-15% in treated females. Eight per cent of male controls had tumours and between 16-23% of treated males. Incidences of endocrine organ tumours were comparable in all groups. A hepatoma was found in 1 female and 1 male led 180 ppm Dieldrin. The present results show that hamsters tolerate higher doses of Dieldrin than do mice and rats. No significant tumour incidence was observed in treated versus control Syrian golden hamsters.

Lack of carcinogenicity of DDT in hamsters.

Syrian golden hamsters were fed for their lifespan a diet containing 0, 125, 250 and 500 parts per million (ppm) of ddt. The incidence of tumour bearing animals was 13% among control females and ranged between 11-20% in treated females. In control males 8% had tumours. The incidence of tumour bearing animals among treated males ranged between 17-28%. The incidence of adrenal cortex tumours showed a dose-related increase among the DDT-treated males. A liver-cell tumour and 2 liver hemangioendotheliomas were observed in 3 males treated with 250 ppm DDT. No liver-cell tumours were observed in the controls. No significant difference in tumour incidence was observed in treated versus control Syrian golden hamsters.

Effects of long-term intake of DDT on rats.

DDT is a pesticide used in malaria-control programmes throughout the world. Its potential carcinogenicity was studied in MRC Porton rats (Wistar-derived) which received dietary concentrations of 0, 125, 250 and 500 parts per million DDT (technical-grade) for life. The treatment had no adverse effects on body growth or survival rate. Various types of tumours were observed in animals in all groups: exposure to DDT resulted in statistically significant increased incidence of liver-cell tumours only in female treated rats; one such tumour was observed in control rats. No metastases of these tumours were found.