Enhanced Expression of Calcium-binding Protein Regucalcin MRNA in Regenerating Rat Liver

The expression of hepatic calcium-binding protein regucalcin mRNA was investigated in regenerating rat liver. The change of regucalcin mRNA levels was analyzed by Northern blotting, using liver regucalcin cDNA (0.9 kb with complete open reading frame). The reduced liver weight by partial hepatectomy (about 70%) was completely restored at 3 days after surgery. Regenerating liver significantly increased calcium content. Liver regucalcin mRNA levels clearly increased 1-5 days after hepatectomy, in comparison with that of sham-operated rats, although the increase was not seen 12 hr after the surgery. Increased regucalcin mRNA levels in regenerating liver were appreciably reduced by single intraperitoneal administration of actinomycin D (100 micrograms/100 g body weight), an inhibitor of transcriptional process. Moreover, the increased regucalcin mRNA levels by hepatectomy was weakened by a single intraperitoneal administration of trifluoperazine (2.5 mg/100 g), an inhibitor of Ca2+/calmodulin. These findings demonstrate that the expression of hepatic regucalcin mRNA is enhanced in regenerating rat liver.