Effects of insulin and norepinephrine added in vitro on the metabolism of brown adipose tissue in the absence of added glucose

Rat interscapular brown adipose tissue slices incubated with succinate as substrate can be stimulated by norepinephrine to exhibit a rate of oxygen consumption that appears to exceed by a wide margin that reported for any other rat tissue under any conditions in vitro. This further supports the concept of brown adipose tissue as a specialized site of heat production. Brown adipose tissue slices under maximal stimulation by norepinephrine and incubated in the absence of added substrate consume oxygen linearly and at a high rate for at least 14 hr. This is taken as further evidence that stored lipid can act as the major fuel to support the vigorous oxidative metabolism of which this tissue is capable. This unusually stable preparation appears to be attractive as a system for the study of relatively long-term effects of hormones in vitro. Brown resembles white adipose tissue in that insulin exerts an antilipolytic effect on both types of tissue in Krebs-Ringer phosphate buffer in the absence of added glucose. On the other hand, insulin stimulates the oxygen consumption of brown but not white adipose tissue under these conditions. A procedure is described for the rapid and nearly quantitative removal of the interscapular brown adipose tissue from a rat, virtually free of contamination by muscle or white adipose tissue. One of nine papers to be published from the Symposium “Brown Adipose Tissue,” presented at the AOCS-AACC Joint Meeting, Washington, D.C., March 1968.