Altered gene expression of hepatic lanosterol 14alpha-demethylase (CYP51) in lead nitrate-treated rats.

Effects of lead nitrate (LN), a hepatic mitogen, on hepatic gene expressions of lanosterol 14alpha-demethylase (CYP51) and the sterol regulatory element binding proteins (SREBP-1a, SREBP-1c and SREBP-2), which are thought to be transcription factors for hepatic CYP51 gene, were examined by the methods of Northern blot and/or real time reverse transcriptase-polymerase chain reaction (RT-PCR). In both immature (4-week-old) and mature (7-week-old) rats, LN treatment resulted in definite increases in hepatic gene expression of CYP51 at 12 h and in the liver weight at 48 h. As for transcription factors for the CYP51 gene, enhanced gene expression of SREBP-2 was observed 6-12 h after LN treatment, whereas no enhanced gene expression of other SREBPs, SREBP-1a and SREBP-1c, was observed at any time after the treatment; for SREBP-1a, there was no significant change; for SREPB-1c, there was a drastic decrease. In addition, the serum total cholesterol level was increased 12 h after LN treatment to 7-week-old rats, and the increased level was maintained at least up to 48 h later. In the present study, we demonstrate for the first time that LN, a heavy-metal ion, activates the expression of the SREBP-2 and CYP51 genes without decreasing the serum total cholesterol level and further suggest that only SREBP-2 among SREBPs might play an important role in the LN-enhanced CYP51 gene expression.