Meeting Abstract

22.5  Jan. 5  Reserve capacities of internal organs in laboratory mice divergently selected for basal metabolic rate (BMR) KSIAZEK, A.*; KONARZEWSKI, M.; CZERNIECKI, J.; University of Bialystok, Bialystok, Poland; University of Bialystok, Bialystok, Poland; University of Bialystok, Bialystok, Poland anetak@uwb.edu.pl

BMR is considered to reflect energetic costs of maintenance of metabolically active internal organs. We examined whether BMR also reflects the costs of maintenance of reserve capacity of these organs to withstand sudden metabolic stress, using as a animal model laboratory mice from two lines divergently selected for high and low BMR. We suddenly transferred mice of both lines from an ambient temperature of 23�C to 5�C. Cold stress elicited an increase in food intake, which was significantly higher in high (H-BMR) than in low (L-BMR) line and simultaneous similar reduction of food digestibility in both lines. Cold-exposure also elicited a considerable increase in masses of internal organs (small intestine, heart and kidneys), however smaller in L-BMR than in H-BMR mice. It did not affect the mass of liver. The metabolic load on small intestine (quantified as the ratio of food consumption to organ mass) was significantly higher in L-BMR line. In contrast, the metabolic load on liver, kidneys and heart (quantified as the ratio of energy assimilation to organ mass) was significantly higher in H-BMR line. However, the latter was associated with an increase of activity of citrate synthase in these organs, which was higher in H-BMR line. We conclude that L-BMR mice subject to sudden cold stress were close to exhaustion of their reserve capacities, whereas H-BMR mice were able to quickly restore them. Thus, high BMR may be adaptive under unpredictable environmental conditions.