Non-shivering thermogenesis in a carnivorous marsupial, Sarcophilus harrisii, in the absence of UCP1

Abstract

The presence of, and the physiological mechanisms behind, non-shivering thermogenesis (NST) were investigated in the Tasmanian Devil ( Sarcophilus harrisii, Boitard 1841). This was performed by measuring metabolic rate in response to cold exposure with and without an injection of norepinephrine. We also attempted to identify the presence of uncoupling protein 1 (UCP1) and its involvement (if any) in NST in S. harrisii, prior to and after cold exposure. UCP1 is a specialized protein channel found within the mitochondria of brown adipose tissue that is known to be involved in eutherian NST. Increase in resting oxygen consumption (VO 2), were measured under constant conditions at 20°C after various stimuli; long-term cold exposure (14 days at 2–3°C), and with or without subsequent norepinephrine injection was used to indicate the presence of NST. Concurrent with the functional studies, molecular level studies including Western blots and RT-PCR were used to identify the expression of UCP1. We found that injection of norepinephrine significantly increased NST after cold exposure in S. harrisii. The post-acclimation resting (VO 2) increased by 11%, whereas the combination of cold exposure and injection of NE elicited an approximately 30% increase in metabolic rate. However, expression of UCP1 in S. harrisii was not identified by the molecular techniques employed, in either the pre- or post-cold-acclimated tissues. These data suggest that S. harrisii shows NST ability and that it is accomplished in the absence of UCP1.