Synergistic effect of β-cryptoxanthin and zinc sulfate on the bone component in rat femoral tissues in Vitro: The unique anabolic effect with zinc

Abstract

The effect of the combination of β-cryptoxanthin and zinc sulfate (zinc) on bone components in the femoraldiaphyseal and -metaphyseal tissues of young rats in vitro was investigated. Bone tissues were cultured for 48 h in a serum-free Dulbecco's modified Eagle's medium containing either vehicle, β-cryptoxanthin (10-9-10-7M) or zinc sulfate (10 -6-10-4M). The presence of β-cryptoxanthin (10 -9M) or zinc (10-6M) did not have a significant effect on calcium content in the femoral-diaphyseal or -metaphyseal tissues. However, culture which combined bcryptoxanthin (10-9M) and zinc (10 -6M) caused a significant increase in calcium content in the femoral-diaphyseal and -metaphyseal tissues. Such an effect was not observed by the combination of β-cryptoxanthin (10-9M) plus genistein (10-6M) or menaquinone-7 (10-6M), or zinc (10 -6M) plus genistein (10-6M) or menaquinone-7 (10 -6M). Also, the combination of β-cryptoxanthin (10 -9M) plus zinc (10-6M) caused a remarkable increase in alkaline phosphatase activity and deoxyribonucleic acid (DNA) in the femoral-diaphyseal and -metaphyseal tissues, while their application alone did not have an effect on the enzyme activity or DNA content in the femoral tissues. The effect of the combination of β-cryptoxanthin (10-9M) plus zinc (10-6M) in increasing calcium content, alkaline phosphatase activity, and DNA content in the femoral-diaphyseal and -metaphyseal tissues was completely prevented in the presence of cycloheximide (10-6M), an inhibitor of protein synthesis, or 5,6-dichloro-1-β-D- ribofuranosylbenzimidazole (DBR), an inhibitor of transcriptional activity. This study demonstrates that the combination of β-cryptoxanthin and zinc at a lower concentration has a synergistic effect on bone components in vitro. © 2005 Pharmaceutical Society of Japan.