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.