TELEMETRIC MEASUREMENT OF BODY
TEMPERATURE IN TRANSGENIC MICE
WITH ABLATION OF BROWN ADIPOSE TISSUE

H. Münzberg, G. Heldmaier, S. Klaus,
Fachbereich Biologie/ Zoologie, Philipps-Universität, D - 35032 Marburg

INTRODUCTION In these transgenic mice the diphteria toxin A sequence was inserted in the promotor region of the uncoupling protein (UCP) which is only expressed in brown adipose tissue (BAT) (Lowell at al. 1993). This causes a 68% ablation (decrease of UCP) of brown adipose tissue. BAT is a heat producing tissue which is only found in mammals. It is important for the maintainance of body temperature especially in small mammals (Smith, 1961 and Nechad, 1986). Furthermore it is involved in the control of body weight (Rothwell and Stock, 1979). The transgenic mice with ablated BAT support this conclusion, since the ablation was accompanied by obesity. This obesity apparently developped without a compensatory hyperphagia (Lowell et al. 1993). Studies in our group recently showed that even the efficiency of food resorption was not different between transgenic and control mice (C. Trülof, 1996).

METHODS Temperature transmitter (Mini Mitter) were used to measure body temperature (T_b). The transmitters were implanted into the abdominal cavity. T_b was recorded continuously and without handling the mice. The signals were received through an arial at the bottom of the cage by ordinary AM-radio. An interface (AD-transformer) transformed the radio-signals for the computer. In this study 6 mice were measured simultanously in 6 minutes intervals. Data collection as well as scanning of different channels was controlled by software developped in our group.

RESULTS T_b was recorded for 8 days in 6 mice - 3 transgenic mice, 3 control mice. Both - transgenic and control mice - showed a circardian rhythm with a temperature peak at the beginning of the dark phase. But the transgenic mice had a significantly lower level of body temperature (T_b) at 35,5°C (transgenic mice) instead of 36,4°C (control mice).

DISCUSSION This result indicates that transgenic mice may have lower energy requirements as compared to controls at the same ambient temperature. These reduced energy requirements for thermoregulation at a constant food intake may contribute to the development of obesity.