US EPA

2142864 

Journal Article 

Review 

Use of newborn and infant animals in carcinogenicity testing 

Della Porta, G 

1968 

1 

Food and Cosmetics Toxicology
ISSN: 0015-6264
EISSN: 1878-6049 

NIOSH/00160474 

6 

2 

243-252 

English 

4299531 

10.1016/0015-6264(68)90205-8 

The use of newborn and infant animals in carcinogenicity testing is discussed. Ever since the study of chemical carcinogenesis was first undertaken, it has been known that age is a factor influencing the incidence of tumors; the sooner in life dosing is started, the stronger the carcinogenic response. For example, 30 to 100 micrograms (microg) 7,12-dimethylbenz(a)anthracene (57976) when injected subcutaneously or intraperitoneally into various strains of mice within 24 hours of birth causes lymphosarcoma incidences of 15 to 80 percent. When it is given to 4 week old Swiss-mice at doses of 100 or 1,000microg, tumor incidences of only 3 and 20 percent, respectively, occur. The incidences of lung adenomas and hepatomas are also significantly influenced by dosing at birth or during the suckling age. It is noted that at the time of birth, the liver cell assumes a number of new functions. Among these functions, detoxication has great importance for the newborn organism, since the enzymes responsible for the various mechanisms of detoxication have low activity. It is likely that impaired or slow detoxication is the major factor accounting for the specific susceptibility of the newborn liver to carcinogenesis. The author recommends that of the two rodent species usually employed in carcinogenesis tests, infant mice should be used for short treatment and rats for prolonged studies.