text: << 4-chloro-6-[(2,3-xylidine)-pirimidinylthio] acetic acid >> (WY-14,643), a specific ligand of the PPAR-alpha subtype, causes the most dramatic increase in [[ UCP-3 ]] mRNA, whereas troglitazone, a specific activator of PPAR-gamma, also significantly increases UCP-3 mRNA abundance in skeletal muscle of lactating mice.