AJP - Endocrinology and Metabolism, Vol 254, Issue 3 E378-E383, Copyright © 1988 by American Physiological Society
Mitochondrial membrane transitions in heart and other organs of a hibernator
J. K. Raison, M. L. Augee and R. C. Aloia
CSIRO Division of Food Research and School of Biological Sciences, Macquarie University, North Ryde, New South Wales, Australia.
Critical temperatures (T) for transitions in both lipid structure and
enzyme function of mitochondrial membranes from liver, kidney, brown fat,
and heart tissues were determined for the hibernator Spermophilus lateralis
at two weekly intervals from early summer to late autumn and during
hibernation. For all tissues T fell into one of three groups: those below 4
degrees C (the minimal level of accurate determination), those centered
about a mean of 11.9 +/- 1.4 degrees C, and those centered about a mean of
20.9 +/- 1.8 degrees C. The T for tissues from torpid animals and from
heart, at all sampling periods, was below 4 degrees C. For liver, kidney,
and brown fat the mean T was approximately 21 degrees C in early summer but
was lowered later in the season in a two-step process, falling to below 4
degrees C before the animals were exposed to cold and entering torpor. It
is concluded that for mitochondria the thermal response of the membrane
lipids is altered such that the transition in structure and function is
always below the minimum body temperature likely to be experienced by this
animal. Heart tissue is exceptional in that the transition is at a
temperature consistent with a body temperature of torpor even in
summer-active animals.
