The hairless-obese mouse

Viable mice homozygous for two recessive autosomal genes, hairless (hr) and obese (ob) were produced with an average life span of 538 +/- 34.1 days. On the average, hairless-obese mice weighed about 73 percent as much as obese mice. Since obese mice consumed approximately 73 percent as much oxygen per gram body weight per hour as hairless-obese mice at about 24 degree C, the weight averages appear to be closely inversely related to the oxygen consumption averages. The presence or absence of pelage seems to make a negligible contribution to oxygen consumption in these two types of obese mice. The hairless condition of the hr/hr genotype seems to contribute to increased oxygen consumption beyond that expected as a consequence of their lower average body weight. The average oxygen consumptions for seven female mice in each of four phenotypic groups (hairless, normal, hairless-obese, and obese) were 3.87, 3.12, 2.39, and 1.74 ml/g/hr, respectively. The two mutants appear to interact in a simple additive way and not as a mutant suppression system. On an absolute basis, the hr/hr genotype seems to have approximately 54 percent as much affect on oxygen consumption as the ob/ob genotype. Litter records at about 60 days of age for four kinds of matings did no reveal any statistically significant deviations from expected ratios.