Thermogenic responses to body cooling during fever induced by Staphylococcus aureus cell walls in rabbits |
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Authors: | Ø Tøien J B Mercer |
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Institution: | Department of Arctic Biology and Institute of Medical Biology, University of Troms?, N-9037 Troms?, Norway Tel.: +47 776 45661, Fax:+47 776 80706, e-mail: oivindt@fagmed.uit.no, NO
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Abstract: | Hypothalamic temperature (T
hypo) and metabolic heat production (M) were measured in seven conscious rabbits injected intravenously with either saline or
with Staphylococcus aureus, (8 · 107 cell walls · kg−1) while being subjected to a 3-h period of ramp-like total body cooling using a chronically implanted intravascular heat exchanger.
In pyrogen-injected animals cooling started (1) at the time of injection or (2) 70 min after injection. In (1) the fall in
T
hypo induced by heat extraction was similar (1.0 °C) in afebrile and febrile animals. In (2) there was a transient increase in
T
hypo of about 0.5 °C at a time corresponding to the start of fever resulting in a significantly smaller fall in T
hypo at the end of the 3-h cooling period (0.5 °C vs 0.9 °C, P < 0.05, n = 5). At this time in both (1) and (2) M was lower than theoretically expected from the increase in shivering threshold during
fever. However, most of this effect can be explained when available data showing a decrease in thermosensitivity during S. aureus-induced fever are taken into account. After cessation of cooling in both groups of febrile animals T
hypo rose to about 1 °C higher than the precooling level, which is comparable to the fever level in a separate series of experiments
with S. aureus injection without cooling (1.2 °C).
Accepted: 23 September 1997 |
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Keywords: | Temperature regulation Gram-positive bacterial cell walls Hypothermia Pyrogen Shivering thermogenesis |
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