The noradrenaline-induced energy dissipation rate was measured with a direct microcalorimeter in brown adipose tissue taken from rats acclimated to 34 degrees C (HA), perchlorate treated (PC) and heat acclimated-perchlorate treated (HAPC). The response to 10(-7) M NA was reduced by 45%, 47% and 86% in HA, PC and HAPC groups, respectively, as compared to a control group kept at 24 degrees C. In the same groups, the response to 10(-6) M NA was reduced by 34%, 7% and 64%, respectively.
Resting oxygen consumption measured at neutral temperature was reduced, with respect to control, by 23, 27, and 34% in heat acclimated, perchlorate treated, and heat acclimated-perchlorate treated rats, respectively. Administration of 0. 4 mg NA/kg increased oxygen consumption by 40, 30, 5 and 1% above resting level in control, heat acclimated, perchlorate treated, and heat acclimated-perchlorate treated rats, respectively.