Sexual difference of hepatic calcium-binding protein regucalcin mRNA expression in rats with different ages: effect of ovarian hormone.

The sexual difference of calcium-binding protein regucalcin mRNA expression in the liver of rats was investigated by Northern blot analysis. Liver regucalcin cDNA (0.9 kb of open reading frame) was used as a probe. The analysis of total RNAs extracted from various tissues of rats indicated that regucalcin mRNA was present primarily in the liver with a size of 1.8 kb. Hepatic regucalcin mRNA was expressed in male rats more than in females. This sexual difference was also seen in aged rats (50 weeks old), although the expression was decreased with increasing age. Ovariectomy did not cause a significant alteration in hepatic regucalcin mRNA levels. The subcutaneous administration of 17beta-estradiol (0.2 mg/100 g body weight) in ovariectomized rats did not cause an appreciable increase in hepatic mRNA levels. The results demonstrate that regucalcin mRNA expression in rat liver is based on sex, and that this difference may not be related to estrogen.