Description_x000D_ Biochem/physiol Actions_x000D_ Liver X receptors (LXRs) are nuclear receptors that regulate the metabolism of cholesterol and bile acids. There are two subtypes of LXRs, LXRα and LXRβ. LXRα is preferentially expressed in liver, small intestine, kidney and spleen. In contrast, LXRβ expression is ubiquitous. The genomic structure and the promoter regions of the two LXR genes contain specific regulatory sites, which suggest that LXRs may have physiological roles in the immune system. Like other nuclear receptors, LXRs heterodimerize with retinoid X receptor (RXR) for function. LXRs are activated by naturally occurring oxysterols and regulate the expression of target genes, including ATP binding cassette transporter 1 (ABC1), ATP binding cassette transporter 8 (ABC8) and cholesterol ester transfer protein (CETP). LXRα is thought to play a major role in the control of cholesterol catabolism by stimulating the expression of cholesterol 7-α-hydroxylase (CYP7A1), the rate limiting enzyme of bile acid synthesis._x000D_ Physical form_x000D_ Clear and colorless frozen liquid solution_x000D_ Preparation Note_x000D_ Use a manual defrost freezer and avoid repeated freeze-thaw cycles. While working, please keep sample on ice.