Inhibitory Effect of Marine Alga Sargassum horneri Extract on Bone Resorption in Tissue Culture in Vitro

Abstract

The effect of marine alga Sargassum horneri extracts on bone resorption in vitro was investigated. Femoral-diaphyseal and -metaphyseal tissues obtained from normal rats were cultured for 48 hr in Dulbecco's modified Eagle's medium (high glucose, 4.5%) supplemented with antibiotics and bovine serum albumin. The experimental cultures contained water-solubilized extracts (10, 25, and 50 μg/ml of medium) of S. horneri. The bone-resorbing factors parathyroid hormone (1-34) (PTH; 10^-7 M) and prostaglandin E₂ (PGE₂; 10^-5 M) caused a significant decrease in the diaphyseal and metaphyseal calcium content. The decrease in bone calcium content induced by PTH or PGE₂ was completely inhibited by water-solubilized extracts (10, 25, and 50 μg/ml) of S. horneri. In addition, these extracts (25 and 50 μg/ml) completely prevented the PTH (10^-7 M)- or PGE₂ (10^-5 M)-induced increase in medium glucose consumption and lactic acid production by bone tissues. Moreover, S. horneri extracts (10-50 μg/ml) blocked PTH (10^-7 M)- increased acid phosphatase activity in the diaphyseal and metaphyseal tissues. These findings indicate that water-solubilized extracts of S. horneri have a direct inhibitory effect on bone resorption in tissue culture in vitro.