Table 7.
Rates of resting oxygen consumption by major tissues of fasted adult rats1
| Whole-body or specific tissue | Body weight or tissue weight in a 300-g adult rat (g)2 | O2 consumption | Heat production | ||||
|---|---|---|---|---|---|---|---|
| Rate (ml/100 g/min)1 | Total O2 consumption (ml/300 g rat/min) | % of whole body O2 consumption | Rate (Kcal/100 g/h)3 | Total heat production (Kcal/300 g rat/h) | % of whole body heat production | ||
| 2.0 | 6.0 | --- | 0.576 | 1.73 | --- | ||
| BAT | 0.61 | 48 | 0.293 | 4.9 | 13.8 | 0.084 | 4.9 |
| Heart | 1.53 | 19.4 | 0.297 | 5.0 | 5.59 | 0.086 | 5.0 |
| Kidneys | 2.63 | 19.1 | 0.502 | 8.3 | 5.50 | 0.145 | 8.4 |
| Liver | 10.8 | 15.9 | 1.72 | 28.7 | 4.58 | 0.495 | 28.6 |
| Brain | 1.61 | 10.3 | 0.166 | 2.8 | 2.97 | 0.048 | 2.8 |
| Small intestine | 6.10 | 6.4 | 0.390 | 6.5 | 1.84 | 0.112 | 6.5 |
| Spleen | 0.77 | 2.2 | 0.017 | 0.28 | 0.63 | 0.0049 | 0.28 |
| Testes | 3.58 | 1.7 | 0.061 | 1.0 | 0.49 | 0.018 | 1.0 |
| Lungs | 1.63 | 1.0 | 0.016 | 0.27 | 0.29 | 0.0047 | 0.27 |
| Skeletal muscle | 135 | 0.92 | 1.24 | 20.7 | 0.27 | 0.358 | 20.7 |
| WAT | 33.9 | 0.18 | 0.061 | 1.01 | 0.052 | 0.018 | 1.01 |
The mean body weight of male Sprague-Dawley rats was 300 g (275 – 325 g). Rats were fasted for 16 h before rates of oxygen consumption by the whole body, kidneys, liver and small intestine were made (66). Perfused hindlimb and cardiac preparations were used to determine O2 consumption by resting skeletal muscle (71) and working hearts respectively (72). Rates of O2 consumption by rat brain (73) and brown adipose tissue (75) are taken from the literature. Rates of O2 consumption by rat lungs, spleen and testes are taken from the literature (74). The rate of O2 consumption by white adipose tissue is estimated at 20% of that for resting skeletal muscle (59). The rate of O2 consumption by the rat is expressed as ml/100 g body weight/min. The rates of O2 consumption by tissues are expressed as ml/100 g wet tissue weight/min.
Male Sprague-Dawley rats (Charles River Laboratories) were fed a low-fat diet (12) between 4 and 8 weeks of age. Tissues were obtained from 8-week-old rats after they were fasted for 16 h. The mean body-weights of rats were 308 and 301 g before and after a 16-h fast, respectively. BAT, brown adipose tissue; WAT, white adipose tissue.
Heat production was calculated as 4.8 cal (or 20.1 J) heat generated per 1 ml O2 consumed by the body or tissue (60). The rate of heat production by the rat is expressed as ml/100 g body weight/h. The rates of heat production by tissues are expressed as ml/100 g wet tissue weight/h.