Hepatic calcium-binding protein regucalcin is released into the serum of rats administered orally carbon tetrachloride

The change in calcium-binding protein regucalcin, mainly localized in liver, in the liver and serum of rats received a single oral administration of carbon tetrachloride (50%; 1.0 ml/100 g body weight) was investigated. The change of regucalcin mRNA levels in the liver was analyzed by Northern blotting using liver regucalcin cDNA (0.6 kb). At 10 and 24 h after the administration, liver regucalcin mRNA levels were reduced markedly. Moreover, regucalcin concentration in the liver and serum was estimated by enzyme-linked immunoadsorbent assay (ELISA) with rabbit-anti-regucalcin IgG. Administration of carbon tetrachloride (CCl₄) induced a significant decrease in liver regucalcin concentration and a corresponding elevation of serum regucalcin concentration at 24 h after the administration. An appreciable increase in serum regucalcin concentration was seen at 2 h after the administration. Meanwhile, serum transaminases (GOT and GPT) activities were significantly increased by CCl₄ administration, indicating that liver injury is induced. The present study demonstrates that hepatic regucalcin is released into the serum of rats administered orally CCl₄, suggesting that the estimation of serum regucalcin is a useful tool for diagnosis of liver injury.