CHEMICAL THERMOGENESIS IN THE FUNCTIONALLY EVISCERATED COLD-ACCLIMATED RAT

Abstract

The effect of functional evisceration (ligation of rectal colon, superior mesenteric and coeliac arteries, and portal vein) on the rise in oxygen consumption by rats which have been acclimated at 30° and at 6 °C. and then anesthetized or curarized and exposed to 6 °C. has been examined. At 30 °C., the O2 consumption of anesthetized cold-acclimated rats was higher than that of anesthetized warm-acclimated rats, but after functional evisceration there was no significant difference between the lower levels of O2 consumption obtained in the two groups. In anesthetized warm-acclimated rats the increase in O2 consumption in the cold after evisceration was smaller than that seen after sham-operation but both increases were suppressed by injection of tubocurarine. Anesthetized cold-acclimated rats, whether eviscerated or sham-operated, gave essentially the same increase in O2 consumption when exposed to 6 °C. and injection of tubocurarine did not lower the O2 consumption to the levels observed before the cold-induced rise took place. In cold-acclimated curarized rats, functional evisceration before exposure to cold did not always prevent increases in O2 consumption but the average increase was not significant in the group. Also, functional evisceration after increase in O2 consumption had taken place in cold-acclimated curarized rats exposed to 6 °C. did not immediately lower the O2 consumption to the level observed after evisceration at 30 °C. It is concluded that the presence of the abdominal viscera is not essential for the manifestation of chemical thermogenesis in the cold-acclimated white rat.