Cancer of the Urinary Bladder Induced in Mice with Metabolites of Aromatic Amines and Tryptophan

Abstract

SENSITIVITY of the bladder epithelium to carcinogenic stimuli was demontrated by the induction of cancer following the introduction of coal tar directly into the bladders of rats (Maisin and Picard, 1924;Picard, 1927). Bonser, Clayson, Jull and Pyrah (1953) showed that the implantation of relatively large paraffin wax pellets without added chemicals into the bladders of rats induced papillomas.On the other hand Rudali, Chalvet and Winternitz (1955) were unable to obtain tumours when small pellets of paraffin wax or cholesterol were inserted into the bladders of rats, but carcinomata were produced with wax or cholesterol pellets containing phenazine, 1: 2-5: 6-dibenzphenazine or 20-methylcholanthrene.The bladders of mice seem to be more resistant to the apparent carcinogenic; action of inert solids than are those of rats so that mice are more suitable animals for the testing of bladder carcinogens.Jull (1951) developed the technique of surgical introduction of wax pellets containing carcinogens into the bladders of mice and this has been used very effectively by Bonser, Clayson and Jull (1951) and by Bonser, Clayson, Jull and Pyrah (1952) in studying the induction of bladder cancer. These authors found that 2-naphthylamine, which induces bladder cancer in dogs and man, does not cause cancer when introduced into the bladders of mice. On the other hand pellets containing 2-amino-l-naphthol, which is a known intermediary metabolite of 2-naphthylamine, produced cancer of the bladder. Thus they showed that the method could give some indication as to whether a carcinogen was acting directly or after metabolic changes. The fact that bladder tumours were obtained with 20-methylcholanthrene and 3: 4-5: 6-dibenzcarbazole suggests that these polycyclic compounds act without undergoing previous metabolic changes.In the present work the technique described by Jull (1951) has been modified in two ways (cf. Boyland and Watson, 1956). Firstly, the substances under test are mixed with four parts of cholesterol and compressed into pellets instead of being mixed with molten wax. Secondly, the opening in the bladder through which the pellet is introduced is tied off with thread instead of being sewn. A disadvantage of this method is that some tumours are induced by cholesterol pellets alone and this must be considered in assessing the carcinogenicity of the substances tested. Bonser, Bradshaw, Clayson and Jull (1956), in a thorough investigation of this technique, obtained tumours in a proportion of mice treated with pellets of paraffin wax. This induction of cancer by chemically inert material is perhaps analogous to the induction of sarcomata by subcutaneous implantation *Present address: Brisban)e General Hospital, Brisbane, Australia.

The Testing of Ortho Hydroxy-Amines and Related Compounds by Bladder Implantation and a Discussion of their Structural Requirements for Carcinogenic Activity

“…Adoption of the modified operative technique of Allen et al (1957) considerably reduced the post-operative mortality, and improved survival of the mice during the experimental period was achieved by the control of ectromelia by vaccination. Of 430 mice which lived for 25 weeks after operation 16 (3.7 per cent) died or were killed in extremis at 25-30 weeks, 4 (0.9 per cent) at 31-34 weeks, 22 (5.1 per cent) at 35-39 weeks, while 388 (90.2 per cent) lived to the full 40 weeks of the experiment.…”

“…Allen et al (1957) tested twenty-six compounds but with few exceptions the number of animals used were below the minimum for the confident acceptance of their results. Using this information it is possible to assess the value of the hypothesis put forward by Clayson (1953) that " compounds which contain a hydroxyl and an amino group ortho to each other in an aromatic system containing two or Ortho hydroxy-amines with aromatic systems containing two or more rings are generally found to be carcinogenic when tested by bladder implantation.…”

“…The pellets were made by compression from an intimate mixture of cholesterol and the chemical (12.5 per cent) under test and were implanted by the method of Jull (1951) as modified by Allen et al (1957). The results were interpreted by the oriteria described by Bonser and Jull (1956).…”

“…The results showed that although pellets containing the aromatic amines, 2-naphthylamine and 4-aminodiphenyl, induced a slightly higher incidence of -tumours than did the vehicle alone, the derived ortho hydroxy-amines, 2-amino-1-naphthol hydrochloride and 3-hydroxy-4-aminodiphenyl sulphate, induced a significantly higher yield of tumours. The results from the other compounds tested supported the hypothesis (Clayson, 1953) that the ortho hydroxy-amines are carcinogenic metabolites of the aromatic amines.Bonser, Bradshaw, Clayson and Jull (1956) used paraffin wax as the base for their pellets, whereas Boyland and Watson (1956) and Allen, Boyland, Dukes, Horning and Watson (1957) used cholesterol and suggested that it was preferable. The purpose of the present experiments was firstly to investigate further the use of cholesterol as a base for bladder implantation and secondly to test additional compounds for carcinogenic activity by this method.…”

“…Bonser, Bradshaw, Clayson and Jull (1956) used paraffin wax as the base for their pellets, whereas Boyland and Watson (1956) and Allen, Boyland, Dukes, Horning and Watson (1957) used cholesterol and suggested that it was preferable. The purpose of the present experiments was firstly to investigate further the use of cholesterol as a base for bladder implantation and secondly to test additional compounds for carcinogenic activity by this method.…”