7-dehydrocholesterol reductase is an enzyme that has been implicated in both cholesterol biosynthesis and developmental abnormalities in mammals. Rat DHCR, calculated molecular mass of 54.15-kDa polypeptide, shares a close amino acid identity with mouse and human DHCRs (96 and 87%, respectively)(Bae et al 1999 ). Inherited enzymatic deficiency of 7-dehydrocholesterol-delta7-reductase causes Smith-Lemli-Opitz syndrome (SLO) results cholesterol deficiency. It comprises a characteristic combination of facial features, malformations, and mental retardation ( Nowaczyk et al ).