EXPRESSION OF HEPATIC CALCIUM-BINDING PROTEIN REGUCALCIN MESSENGER-RNA IS DECREASED BY PHENOBARBITAL ADMINISTRATION IN RATS

The effect of phenobarbital on the expression of calcium-binding prote in regucalcin mRNA in rat liver was investigated. The change of reguca lcin mRNA levels was analyzed by Northern blotting using liver regucal cin cDNA (0.9 kb of open reading frame). Phenobarbital (4, 8 and 12 mg /100 g body weight) was intraperitoneally administered to rats 3 times with 24 h intervals, and the animals were sacrificed by bleeding at 2 4 h after the last administration. The hepatic regucalcin mRNA levels were markedly reduced by phenobarbital administration. This decrease w as about 50% of control level with the 12 mg/100 g dose. Moreover, the hepatic regucalcin concentration was significantly decreased by the a dministration of phenobarbital (12 mg/100 g), although the serum reguc alcin concentration was not altered appreciably. Meanwhile, serum tran saminases (GOT and GPT) activities were not increased by the administr ation of phenobarbital (4 and 12 mg/100 g). The present study demonstr ates that the expression of hepatic regucalcin mRNA is decreased by ph enobarbital administration in rats, suggesting that regucalcin does no t have a role in drug metabolism related to phenobarbital.