Meeting Abstract

P2.96  Thursday, Jan. 5  The capacity of non-shivering thermogenesis in bank voles from lines selected for high aerobic metabolism WOJCIECHOWSKI, M.S.*; STAWSKI, C.; JEFIMOW, M.; KOTEJA, P.; Nicolaus Copernicus University, Toruń, Poland; Jagiellonian University, Kraków, Poland; Nicolaus Copernicus University, Toruń, Poland; Jagiellonian University, Kraków, Poland mwojc@umk.pl

Comparative data suggest that high non-shivering thermogenesis (NST) capacity in mammals evolved as a compensatory mechanism for low basal metabolic rate (BMR). We report preliminary results of an experiment testing the hypothesis that NST capacity is negatively correlated with BMR in bank voles (Myodes glareolus). The experiment was done on 32 voles from lines selected for high O₂ consumption achieved during swimming and on 27 voles from unselected, control lines. Compared to control lines, BMR in the selected lines is ~14.6% higher (7.1% after adjusting for differences in body mass, m_b). Non-anesthetized animals exposed to ambient temperature = 27.5 ± 0.5°C were injected with noradrenalin (NA) at a dose of (mg kg^-1) = 2.53 m_b (g) ^-0.4 and their rate of oxygen consumption (VO₂) was measured continuously in an open-flow respirometry system. NST capacity was defined as the highest 4-minute VO₂ after NA-injection. The NST capacity (mean ± SD) did not differ between the selected (3.79 ± 0.78 mlO₂ min^-1) and control lines (3.52±0.79 mlO₂ min^-1; analysis of covariance with m_b as a covariate: p=0.49). We also found no correlation between m_b-adjusted BMR and NST capacity among individuals within the selection groups. Thus, we found no support for the prediction that selection leading to a higher BMR results in a decreased capacity for NST. However, the results may be affected by unusually high locomotor activity of the voles from selected lines, which we observed after NA-injection. We hope to eliminate this factor by undertaking the same experiment on anesthetized voles. This study was supported by a grant from the Polish Ministry of Science and Higher Education N N304 168739 to MSW and N303 275233 to PK, and UJ/INoS DS/BW 757 to PK.