Oxygen consumption of isolated brown adipose tissue adipocytes from 1 interbout euthermia (IBE) animal measured at 10°C. Arrows indicate times at which the following additions were made: cells were added and a basal respiration rate was recorded; norepinephrine (NE) was added to achieve the NE-stimulated rate.
Oxygen consumption of isolated brown adipose tissue mitochondria from 1 IBE animal measured at 10°C using octanoyl carnitine as a fuel. Arrows indicate times at which the following additions were made: Mito, isolated mitochondria; OC, octanoyl carnitine and malate; GDP, guanosine 5′-diphosphate; ADP, adenosine 5′-diphosphate; Oligo, oligomycin.
Uncoupled respiration rates from isolated brown adipose tissue mitochondria using pyruvate (A) and octanoyl carnitine (B) as fuel. Respiration rates of isolated mitochondria were standardized to protein concentration. Values represent means + SE and n = 4 for all groups. Statistical significance between torpor and IBE is denoted with an asterisk (P < 0.05).
Maximal enzyme activity of electron transport system complexes using homogenized, isolated, brown adipose tissue mitochondria assayed at 10°C (A) and 37°C (B) and standardized to protein content. Values are means + SE except where sample size <3, in which case error bars represent range. Sample sizes for 10°C activities are 6 (torpor) and 2 (IBE) for all 5 complexes. Sample sizes for 37°C activities are 9 (torpor) and 7 (IBE) for complexes I–III and V. Sample sizes for complex IV 37°C rates are 5 (torpor) and 2 (IBE). No significant differences were observed between hibernation states for any of the complexes (P > 0.05).
Interaction plots of mitochondrial respiration rates from isolated brown adipose tissue mitochondria at 10°C and 37°C using pyruvate (A) and octanoyl carnitine (B) as fuel. Points connected by a line represent data from the same individual.
Basal (A) and norepinephrine (NE; B)-stimulated oxygen consumption rates of isolated brown adipocytes. Rates are standardized to cell concentration. Values represent means + SE. There were no significant differences between torpor (n = 5) and IBE (n = 4).
Response of oxygen consumption rate to norepinephrine (NE) stimulation in isolated brown adipocytes. The fold change in respiration rate from the basal rate to the NE-stimulated rate was calculated for each individual. Values represent means + SE. There were no significant differences between torpor (n = 5) and IBE (n = 4).