Long-term toxicity study of amaranth in rats using animals exposed in utero.

Groups of 90 (control) and 54 (treated) rats of each sex were given amaranth in their diet to provide daily intakes of 0 (control), 50, 250 or 1250 mg/kg for 111 wk (male) and 112 wk (female) after weaning. The rats had also been exposed to the same dose levels in utero, and their parents were exposed for 60 days before mating. The colouring had no adverse effects on fertility, haematological parameters, serum chemistry or incidence of tumours. All treated animals showed contamination of the fur and red colouring of the faeces and at the high dose only the faecal pellets were poorly formed. Rats in the high-dose group produced more pups, and the average pup weight was lower than that of the controls. Rats of the F1 generation given the highest dose level were slightly lighter than the controls despite a small increase in food and water intake. Both sexes given the highest dose level and males given 250 mg/kg/day had increased caecal weight. High-dose females excreted more protein in the urine after 18 months and on histopathological examination females in all treated groups showed an increased incidence of renal calcification and pelvic epithelial hyperplasia with degenerative changes. It is concluded that amaranth fed to rats at dose levels of up to 1250 mg/kg/day in the diet did not have any carcinogenic effect. However, because of the effect on the kidneys of the females it was not possible to establish a no-untoward-effect level in this study.

Long-term toxicity study quillaia extract in rats.

Groups of 48 male and 48 female rats were fed quillaia extract in the diet at levels of 0 (controls), 0.3, 1.0 and 3.0% for 2 yr. The material had no adverse effects on death rate, water consumption, serum chemistry or haematological parameters or on the incidence of histopathological findings, including tumours. In the males given the 3% dietary level, the death rate, total leucocyte count at wk 108, incidence of kidney lesions and weights of the kidneys, heart and thyroid were all below the control values. These differences were explicable, however, in terms of a lowered body weight consequent on a decreased food intake. It is concluded that, in rats, quillaia extract fed at levels up to 3.0% in the diet did not have any carcinogenic effect. The no-untoward-effect level established in this was 3.0% in the diet, approximately equivalent to an intake of 1.5 g/kg/day.

Ortho-toluene sulphonamide and saccharin in the promotion of bladder cancer in the rat.

The importance of the contaminant OTS in the promoting activity of commercial saccharin on rat bladder neoplasia was investigated. OTS, OTS-free and OTS-contaminated saccharin were administered in the drinking water or diet for 2 years to groups of rats pretreated with an intravesical instillation of MNU; OTS alone and OTS-free saccharin were also given to groups of rats not pretreated with MNU. Administration of OTS was not associated with changes in urinary pH, crystalluria or calculus formation, had no effect on the histology of normal rat bladder, and did not increase the incidence of bladder hyperplasia or neoplasia elicited by pretreatment with MNU. No differences could be found between the effect of OTS-free or OTS-contaminated saccharin on bladders of rats pretreated with MNU. These results indicate that OTS contamination played no part in the reported promoting activity of saccharin on the rat bladder. Administration of saccharin did not increase urinary pH, crystalluria or calculus formation, and failed to promote bladder neoplasia after a carcinogenic dose of MNU, though the numbers of proliferative lesions in the bladder were increased.

The effect of water-soluble chemicals on the growth and mitosis of primary newborn rat kidney cells in culture.

Mass cultures of primary rat kidney cells were exposed briefly to aqueous solutions of 20 chemicals and their subsequent growth rate and mitotic activity measured. Proximate carcinogens, and some chemicals with a defined inhibitory action biochemically, depressed the growth and division of the cultures. Non-carcinogenic compounds and precarcinogens did not interfere with the subsequent growth rate and mitotic activity of the cultures. It is suggested that the possession of growth inhibitory properties could give an indication of the carcinogenic activity of a chemical on a short-term basis.

Cytotoxic carcinogeneic response to monocrotaline pyrrole.

The cytotoxic and carcinogenic effects of MCP, the possible proximate metabolite of the alkaloid monocrotaline, were investigated in rats by the subcutaneous route. Sequential of MCP subcutaneously produced an acute inflammatory reaction with necrosis of the local tissue. A slight delay in connective-tissue repair occurred and markedly enlarged fibroblasts were a distinctive feature of the lesion. Four injection site sarcomas were produced after repeated injection of 60 mug MCP in tricaprylin. Injection of 30 mug MCP in tricaprylin twice weekly gave rise to three local tumours. Controls injected repeatedly with tricaprylin developed two sarcomas at the injection site. The significance of these findings is discussed and it is concluded that MCP is undoubtedly cytotoxic but that its carcinogenic potency is equivocal.

Injection site tumours and preceding pathological changes in rats treated subcutaneously with surfactants and carcinogens.

The sequential histological changes and neoplastic response occurring in the subcutaneous tissue of rats after injection of surfactants or carcinogens were compared. Twice weekly subcutaneous injections of the surfactants Blue VRS and Light Green SF elicited a deranged connective tissue repair with continued proliferation of fibroblasts and extensive collagen desposition. In contrast, the carcinogens N-methyl-N-nitrosourea (MNU) and N-nitroquinoline-N-oxide (NQO) appeared to inhibit connective tissue repair and produce morphologically abnormal fibroblasts. The spectrum of neoplastic response was also found to differ. Surfactants gave rise to local sarcomata only after about 47 weeks, whereas carcinogens produced local sarcomata and adenocarcinomata after 20 and 12 weeks respectively.

Early reactions of the subcutaneous tissue to repeated injections of carcinogens in aqueous solutions.

Four water-soluble carcinogens were injected at the same site subcutaneously into rats, mice or guinea-pigs, twice weekly for 5-8 weeks in order to study the evolution of the early tissue reaction. MNU was injected into rats as 0·1 ml. of 0·5% solution, and into mice as 0·1 ml. of 0·05% solution. NQO was administered to rats (0·1 or 0·2 ml. of 0·25 or 0·1%) mice (0·1 of 0·05%) and guinea-pigs (0·5 of 0·1%). Propane sultone and BEI were administered to rats only, the former as 0·1 ml. of 3% and the latter as 0·5 ml. of 2·0% solution.The principal features of the tissue reaction produced by each of the four compounds in rats were similar and consisted of destruction of subcutaneous tissue, deposition of fibrin and "fibrinoid", an abnormal pattern of fibroblastic proliferation with cytomegaly of some fibroblasts and deposition of mucopolysaccharide but little collagen formation. Moreover, the appearance of fibroblastic proliferation was delayed from the normal 2-5 days to 14-16 days.These features are consistent with the known early effects of carcinogens on proliferating target tissues, and differ considerably from those found in the early reactive lesions to repeated injection of solutions of substances possessing physical properties such as surface activity or hypertonicity, or which precipitate at the injection site.