ABSTRACT
Autopsy data on older Germfree (GF) L-W rats showed the occurrence of solid tumors in liver, endocrine organs, breast, and lung. Pollard and Teah had been the first to report the occurrence of spontaneous tumors in GF rats. Although the apparently ubiquitous presence of virus in GF mice makes for a somewhat “unclean” model, data on the occurrence of tumors confirm, to an extent, the results obtained with GF rats. The absence of casein and other dairy proteins from the diet almost totally prevented the aforementioned kidney pathology, and increased the average life span of both the GF and the CV male L-W rats by several months. In general, the presently available data seem to suggest that, other conditions being comparable, spontaneous tumors occur somewhat less frequently in GF than in CV rats. The same impression is gained from a number of studies with direct-acting carcinogens.
