Lifespan studies on male and female mice and rats under SPF-laboratory conditions

Abstract

270 male and 270 female mice (Tif:MAGf [SPF Tif] and 500 male and 500 female rats (Tif:RAIf [SPF Tif] were observed in a lifespan study under SPF-laboratory conditions. Five animals were housed together in Macrolon cages with specified bedding (granulated soft wood). The animals received pelleted food (Nafag No. 890) and tap water ad libitum. Room temperature and relative humidity were held at 22±2°C and 55±5°C resp. Automatic light control guaranteed a 10 h light and 14 h darkness cycle. The food intake of the rats (in g/kg/day) was between 250 at week 1 and 25 (male) and 33 (female) at the 120th wk. The mean body weight of the rats increased from 53.5 g (male) and 51.3 g (female) at wk one to 1055 g (male) and 631 g (female) at wk 88 and then decreased to 702 g (male) and 472 g (female) at the end of their life expectancy (wk 120 for male and wk 132 for female). Additionally the normal values were established for 100 rats of each sex regarding the hematology, blood chemistry and urinalysis values (totally 44 parameters) at 7, 13, 26, 52, 78 and 104 wk of their life time. The mean life time in days of the male mice was 687 ± 13.9 and of the female mice 766 ± 15.5; of the male rats 711 ± 5.8 and the female rats 765 ± 8. In a total of 237 mice 297 tumours were observed. The most common tumours occurred in the lungs (72 adenomas and 8 adenocarcinomas), followed by ovarian tumours (39), fibrosarcomas (26), malignant lymphomas (31) and tumours of vascular origin (14 haemangiomas and 3 angiosarcomas). Altogether 1210 tumours were found in a total number of 701 rats, 311 of which carried two or more. Primary tumours were found in practically all the tissues. Most common were pituitary adenomas (411 rats), benign (131) and malignant (70) tumours of the mammary tissue and lymphoreticular neoplasms of the thymus (172). The results are discussed with regard to existing recommendations for the performance of chronic toxicity and carcinogenicity feeding studies.