Cellular proliferative capacity and life span in small and large dogs.

In a study comparing animal life spans and in vitro clonal proliferative capacity of skin fibroblasts in groupings of small, middle, large, and very large breeds of dogs of specific ages, the following results were obtained: (1) their life spans were inversely correlated to the frame sizes of the breeds; (2) the percent of large clones present in clone size distributions from the small dogs was inversely proportional to the age of the subjects (this was not true for the large breeds; however, animals older than 8 years were not available in those breeds); and (3) the group composed of the two largest breeds (Great Dane and Irish Wolfhound) had the shortest life spans and also had significantly smaller percentages of large skin fibroblast clones formed in vitro than either of the two groupings of smaller dogs at any age studied. It appears that within the domestic dogs the large body size is accompanied by shorter life span and, in the two largest breeds, decreased cellular growth potential.