Effect of Fructus Ligustri Lucidi on calcium metabolism and vitamin D-dependent gene expressions in ovariectomized rats

Objective: To investigate the effect of Fructus Ligustri Lucidi (FLL), a kidney-tonifying Chinese herbal medicine, on calcium metabolism and vitamin D-dependent gene expression in ovariectomized (OVX) rats. Methods: Four weeks after OVX surgical operation the OVX rats were ig administered with estradiol and FLL for 14 weeks. Ca2+Level in serum, urine, and feces was measured by colorimetric methods, and gene expressions in duodenum and kidney were analyzed by reversed transcriptase-polymerase chain reaction (RT-PCR). Results: Ovariectomy of rat led to significant loss of calcium in vivo, as demonstrated by decreasing serum Ca2+level and increasing Ca2+excretion rate in urine and feces in OVX rat group. Treatment of OVX rats with FLL could effectively restore serum Ca2+level and prevent the increase of Ca2+excretion from urine and feces. RT-PCR Analysis showed that both estradiol and FLL could prevent OVX-induced decrease of mRNA expression in duodenal vitamin D receptor (VDR). In kidney, FLL did not alter mRNA expressions of 25-hydroxyvitamin D 1-hydroxylase (1-OHase) and 25-hydroxyvitamin D 24-hydroxylase (24-OHase), while increased the mRNA expression levels of renal calciumbinding protein-9k (CaBP-9k) and calcium-binding protein-28k (CaBP-28k). Conclusion: FLL could improve the state of calcium imbalance induced by estrogen deficiency and the potential mechanism that contributes to the improvement of calcium status by FLL might involve the increase in intestinal sensitivity to active vitamin D through its up-regulation of VDR expression in duodenum and the enhancement in Ca2+reabsorption via the up-regulation of calcium binding proteins expression in kidney.