Maximum thermogenic response to cold in relation to the proportion of brown adipose tissue and skeletal muscle in the body and to other parameters in young lambs.

No relationship was apparent between the maximum thermogenic response of lambs to cold (summit metabolism) and the dissectable brown adipose tissue content, or the chemically extractable lipid content of the whole animal or the weight of various skeletal muscles. Correlations of summit metabolism with other parameters also suggested that the level of glucose, FFA and glycerol in the circulation, and the glycogen stores in liver and muscle, did not limit summit metabolism. However, significant correlations of summit metabolism with cardiac output and arteriovenous differences in oxygen content of blood focused attention on the possible role of the cardiovascular system and on the metabolic capability of the thermogenic tissues in determining summit metabolism.