Metabolic rate of tissue slices of rats and rabbits as affected by age and body size

Abstract

The studies were carried out by the Warburg technique and the obtained results corrected after establishing by the method of C a s c ar a n o et al. what part of the incubated slices participates in the respiration. Most of the studied tissues from small animals showed higher metabolic rate than the homologous tissues derived from large animals, but the difference was less pronounced than that between basal metabolic rates. The estimated sum of tissue metabolism in young rats approached 100% of their basal metabolic rate, but in the case of adult rats this figure amounted only to 70%>. These results indicate that the metabolism of tissues in vitro is markedly different from their metabolism in vivo. In the author's opinion the main reason for this discrepancy lies in the fast disappearance of the effect of central regulating systems (nervous and humoral) on the metabolic processes occurring in cells of the isolated tissues.

The effects of acclimation to moderate and acute cold in rats

“…This may be inferred from the fact that summated tissue metabolism in vitro is not much different from the basal metabolic rate (BMR) of the intact animal (Field & B e 1 d i n g, 1939; Martin & Fuhrman, 1941;Fuhrman et al, 1961;Jusiak, 1969). Moreover, the metabolic rate of some tissues excised from animals acclimated to low ambient temperature was found to be higher than that of homologous tissues from control animals.…”