Brown adipose tissue in lean and fat selection lines of sheep identified by immunodetection of uncoupling protein in western blots of tissue homogenates

1. Uncoupling protein (UCP) was purified from perirenal adipose tissue of 2-day-old lambs by a procedure involving Triton solubilization and hydroxyapatite treatment. It has an apparent Mr of 34,000. 2. Rabbit anti-sheep UCP and rabbit anti-rat UCP each cross-reacted with both rat and sheep UCP in Western blots, indicating that the major antigenic determinants of the sheep UCP and rat UCP are similar. 3. In Western blots, the anti-sheep UCP showed tissue specificity by detecting a band corresponding to UCP only in brown adipose tissue, but not in heart or liver homogenates. 4. The Western blotting procedure was used to analyse sheep tissues. UCP was detected in samples of perirenal, omental, back and lymph node fat from 2-day-old lambs, but not in heart, liver, muscle or kidney samples. 5. UCP was not detected in any tissue samples from 34-day-old or 7-month-old lambs. 6. Comparison of the amount of UCP in perirenal fat of 2-day-old lambs from lean, fat and control selection lines, using the Western blotting procedure, showed no apparent difference.